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Chromosome locations of non-major histocompatibility complex (MHC) genes contributing to insulin-dependent diabetes mellitus (IDDM) in mice have been determined by outcrossing NOD mice to other inbred strains congenic for the NOD MHC haplotype (H2g7). At least nine non-MHC IDDM susceptibility genes (Idd) were previously identified at first backcross (BC1) after outcross of NOD to C57BL/10.H2g7 congenic mice (B10.H2g7). We investigated whether the same set of Idd loci segregated with IDDM susceptibility after outcross of NOD to NON.H2g7 congenic mice. Since the outcrosses to NON.H2g7 and B10.H2g7 were performed in the same vivarium, direct comparisons were made of the chromosomal locations and relative strengths of Idd alleles in diabetic progeny from the two different outcrosses. In comparison with the NOD x B10.H2g7 outcross, the NOD x NON.H2g7 outcross produced significantly higher IDDM frequencies in F1, F2, and BC1 generations. The high F2 diabetes frequency allowed evaluation of the effects of homozygous expression of both the susceptibility and the resistance allele at Idd loci. This analysis demonstrated that no single non-MHC Idd locus was essential for the onset of diabetes in this cross. After outcross to NON.H2g7, Idd4 (chromosome [Chr] 11), Idd5 (Chr 1), and Idd8 (Chr 14) did not segregate with IDDM in either the BC1 or the F2 generation. Diabetogenic NOD-derived alleles at Idd2 (Chr 9), Idd3 (Chr 3), and Idd10 (Chr 3) were segregating in the BC1. An NON-derived allele contributing to susceptibility on Chr 7 (Idd7) was also detected. Dominant traits, detectable only in the F2 cross, were encoded by Chr 4 (Idd9) and two newly mapped loci on Chr 13 (Idd14) and 5 (Idd15). A third dominant trait was encoded by Chr 6 (possibly Idd6), but here, in contrast to Idd9, Idd14, and Idd15, the NON allele was diabetogenic. Stepwise logistic regression analysis of the BC1 and F2 data confirmed that the ability to identify certainty of the non-MHC Idd loci was contingent on the extent of homozygosity for NOD background genes. This study shows that the diabetogenic phenotype can be achieved through the actions of variable combinations of MHC-unlinked genes and a diabetogenic MHC haplotype.

A low acute insulin response (AIR) is a predictor of non-insulin-dependent diabetes mellitus (NIDDM) in insulin-resistant Pima Indians. We have initiated a search for regions of the genome linked with the AIR using sib-pair linkage analysis as a first step in identifying genes that are determinants of this phenotype. Eighteen short tandem-repeat polymorphisms from chromosome 1 were genotyped in over 900 Pima Indians and tested for linkage with NIDDM and in a subset of Pima Indians for linkage with AIR. The anonymous DNA marker D1S198 on chromosome 1p was linked with AIR (P = 0.000056) in 175 sib pairs from 60 families, all with normal glucose tolerance, but no linkage was observed between D1S198 and NIDDM (P = 0.44, 996 sib pairs). Additional markers genotyped on chromosome 1 did not show linkage with AIR or NIDDM. This study indicates that a locus on chromosome 1p may be a determinant of the phenotypic variation seen in the AIR.

Insulin resistance is believed to be a prediabetic condition that results from reduced rates of insulin-mediated glycogen synthesis in skeletal muscle. A decrease in activities of skeletal muscle glycogen synthase and of its regulatory enzyme type-1 protein phosphatase (PP 1) have been previously identified in insulin-resistant Pima Indians. Because the PP1 catalytic beta-subunit is presumed to be the major isoform in the glycogen-bound PP1 complex, we have selected the structural gene for this subunit (PPP1CB) as a candidate for a detailed genetic analysis. We have determined the exon-intron structure of PPP1CB, and have identified a polymorphic (CA)-repeat marker (D2S1237) at this gene. No sequence abnormalities were detected in PPP1CB by Southern blot analysis or by single-stranded conformational polymorphism analysis of all eight coding exons. Using sib-pair linkage analyses, no evidence for linkage was found between the D2S1237 marker at this locus and fasting insulin, insulin-stimulated glucose uptake in vivo, obesity, or non-insulin-dependent diabetes mellitus. Similarly, we have found no evidence for association of D2S1237 with any of these phenotypes. Based on our data we conclude that the structural gene for the PP1 catalytic beta-subunit does not appear to be a major genetic determinant responsible for the PP1 abnormalities characteristic of insulin resistance in Pima Indians.

The intestinal fatty acid binding protein locus (FABP2) was investigated as a possible genetic factor in determining insulin action in the Pima Indian population. A polymorphism at codon 54 of FABP2 was identified that results in an alanine-encoding allele (frequency 0.71) and a threonine-encoding allele (frequency 0.29). Pimas who were homozygous or heterozygous for the threonine-encoding allele were found to have a higher mean fasting plasma insulin concentration, a lower mean insulin-stimulated glucose uptake rate, a higher mean insulin response to oral glucose and a mixed meal, and a higher mean fat oxidation rate compared with Pimas who were homozygous for the alanine-encoding allele. Since the FABP2 threonine-encoding allele was found to be associated with insulin resistance and increased fat oxidation in vivo, we further analyzed the FABP2 gene products for potential functional differences. Titration microcalorimetry studies with purified recombinant protein showed that the threonine-containing protein had a twofold greater affinity for long-chain fatty acids than the alanine-containing protein. We conclude that the threonine-containing protein may increase absorption and/or processing of dietary fatty acids by the intestine and thereby increase fat oxidation, which has been shown to reduce insulin action.

Insulin-dependent diabetes mellitus (IDDM) in NOD/Lt mice represents a complex polygenic disease. NOR/Lt is a recombinant congenic strain (RCS) in which limited regions of the NOD/Lt genome have been replaced by genome from the C57BL/KsJ strain. NOR mice are insulitis resistant and diabetes free despite genetic identity with NOD at numerous chromosomal regions containing previously described insulin-dependent diabetes (Idd) genes, including the strongly diabetogenic H2g7 major histocompatibility complex (MHC) haplotype. The present study revealed BKs-derived genome on segments of chromosomes (Chr) 1, 2, 4, 5, 7, 11, 12, and 18, approximating 11.6% of the total NOR genome analyzed. (NOD x NOR)F2 segregation analysis was employed to identify chromosomal regions in NOR containing Idd resistance alleles. IDDM developed in 33% (10/30) of F1 females, and 29.3% (36/123) of F2 females aged to 1 yr. A previously unrecognized diabetes resistance locus (designated Idd13r) strongly protective in homozygous state was identified on NOR Chr 2 in linkage with the Il1 alpha structural gene. The existence of this locus was confirmed by construction of a NOD stock congenic for NOR-derived markers on Chr 2. Our analysis shows the utility of RCS and congenic stocks for the identification and isolation of non-MHC genes with strong antidiabetogenic functions.

We characterized the region of human chromosome 4q26-q28 that contains the gene encoding annexin V (placental anticoagulant protein I), a member of a family of calcium-dependent phospholipid binding proteins. A total of 14.5 kb, containing 9 introns, could be directly amplified from genomic DNA; the remainder was characterized from genomic clones in phage lambda and a yeast artificial chromosome. The gene was mapped with restriction enzymes BamHI, EcoRI, HindIII, SacI, StuI, and XbaI; the transcribed region spans 28 kb and contains 13 exons (44 tp 530 bp in size) and 12 introns (0.23 to 8.8 kb in size). Several putative transcription factor binding sites are present in the 5'-region, but the promoter has no recognizable TATA box. This study will facilitate further analysis of the functions of annexin V and its role in disease.

We have identified a novel 69-kD peptide autoantigen (ICA69) associated with insulin-dependent diabetes mellitus (IDDM) by screening a human islet lambda gt11 cDNA expression library with cytoplasmic islet cell antibody positive sera from relatives of IDDM patients who progressed to the overt disease. The deduced open reading frame of the ICA69 cDNA predicts a 483-amino acid protein. ICA69 shows no nucleotide or amino acid sequence relation to any known sequence in GenBank, except for two short regions of similarity with BSA. The ICA69 cDNA probe hybridizes with a 2-kb mRNA in poly(A+) RNA from human pancreas, brain, heart, thyroid, and kidney, but not with skeletal muscle, placenta, spleen, or ovary. Expression of ICA69 was also detected in beta cells and cell lines, as well as in tumoral tissue of islet cell origin. The native ICA69 molecule migrates to 69 kD in SDS-PAGE as detected with specific antibodies. Serum samples from relatives of IDDM patients specifically reacted with affinity-purified recombinant ICA69 on Western blotting. The structural gene for ICA69 was designated ICA1. A homologue in the mouse, designated Ica-1 was mapped to the proximal end of chromosome 6 (within 6 cM of the Met protooncogene). ICA69 adds a novel autoantigen to the family of identified islet target molecules, and by the manner of its identification and characterization large amounts of antigen are available for development of quantitative, convenient predictive assays for autoantibodies and analysis of the role of this molecule in diabetes autoimmunity, as well as its physiologic function.

Insulin action in vivo varies widely in nondiabetic Pima Indians. Not all of this variance is attributable to individual differences in obesity, physical fitness, sex, or age, and after correcting for these co-variates, measures of insulin action aggregate in families. Insulin action at maximally stimulating insulin concentrations has a trimodal frequency distribution, particularly among obese individuals. This is consistent with the hypothesis that a codominantly inherited autosomal gene, unrelated to obesity, determines MaxM in the population. Preliminary sib-pair linkage analyses indicated the possibility of linkage between MaxM and the GYPA/B locus (encoding the MNSs red cell surface antigens) on chromosome 4q. To confirm and extend these findings, 10 additional loci on 4q were typed in 123 siblings and many of their parents from 46 nuclear families. The results indicate significant (P < 0.001) linkage of the FABP2 and ANX5 loci on 4q with MaxM, and of FABP2 with fasting insulin concentration. No linkage was found between the 4q markers and obesity. Our findings indicate that a gene on 4q, near the FABP2 and ANX5 loci, contributes to in vivo insulin action in Pima Indians.

Endogeneous retroviral expression in beta cells is a feature of prediabetes in nonobese diabetic (NOD) mice. The purpose of this study was to characterize the class-specific pattern of retroviral gene expression in NOD/Lt beta cells versus a related, but diabetes-resistant strain, NON/Lt. Electron microscopic comparison of beta cells from both strains indicated low constitutive expression of the intracisternal type A (IAP) retroviral class. However, NOD beta cells, in contrast to NON beta cells, expressed an additional intracisternal retroviral form resembling a type C particle. Antibodies against both IAP and type C were detected in NOD, with the humoral response to type C, but not IAP, preceding decline in beta cell function. RNA was extracted from freshly isolated islets from NOD and NON males. Comparative Northern blot analysis of total type C retroviral gene expression using a gag-pol DNA probe corroborated expression of endogenous type C proviruses in both NOD and NON islet cells and thymus. Use of class-specific retroviral probes identified the class of expressed endogenous retrovirus distinguishing the two inbred strains. The single ecotropic provirus present in both the NOD and NON genome (Emv-30) was not expressed in islets or thymus of either strain. Comparison of endogenous xenotropic provirus content by Southern blot analysis revealed two unique xenotropic loci (Xmv-65, -66) in NOD; 8.4 and 3.0 kb xenotropic envelope (env) RNA transcripts were detected in NOD, but not NON islets and thymus. NON contained three xenotropic loci common to other inbred strains (Xmv-21, -25, and -28). Both strains were partially characterized for content of recombinant (polytropic and modified polytropic) proviruses. IAP RNA expression was common to both NOD and NON islets and hence could not be specifically associated with the unique intracisternal type C particle found in NOD, but not NON beta cells. In conclusion, this study shows that expression of xenotropic type C but not IAP distinguishes retroviral activity in NOD/Lt versus NON/Lt beta cells. The potential pathogenic role of retroviral gene expression in NOD beta cells is discussed.

Homozygosity for the severe combined immunodeficiency (scid) mutation results in a block in T- and B-lymphocyte development. An unusually high incidence of spontaneous thymic lymphoma development was observed after transfer of this mutation from the C.B-17 congenic strain background onto the diabetes-susceptible nonobese diabetic (NOD) background. Thymomagenesis in the NOD-scid/scid mouse was associated with expression of an NOD mouse-unique endogenous ecotropic murine leukemia provirus locus (Emv-30, mapped to proximal region of chromosome 11) not expressed in the standard substrain NOD/Lt thymus. All tumors exhibited insertions of ecotropic proviruses, whereas only a subset also exhibited proviral integrations of mink cell focus-forming retrovirus. Neither class of retrovirus was associated with consistent integration into genes previously associated with activation of oncogenesis. We propose that the unusual features of T-cell ontogeny characteristic of the NOD inbred strain synergize with the scid-imparted block in thymocyte development, leading to activation of the NOD-unique Emv-30 to initiate thymomagenesis.

NOR/Lt is an insulitis-resistant and diabetes-free strain produced from an isolated genetic contamination within an NOD/Lt pedigree line. The albino coat-color phenotype, strain-specific endogenous retroviral profile, and skin graft tests indicated an NOD/Lt x C57BL/KsJ outcross-backcross segregant as the source of the contaminating genome. Analysis of 53 polymorphic DNA, biochemical, and immunologic markers distinguishing NOD/Lt from C57BL/KsJ revealed that 4 chromosomes (chromosomes 2, 4, 11, and 12) in NOR/Lt contained C57BL/KsJ-derived genes. The remaining markers on 14 chromosomes, including the diabetogenic H-2g7 complex on chromosome 17, were of NOD origin. Although completely resistant to cyclophosphamide-induced diabetes, NOR/Lt mice exhibited the same peripheral T-lymphocyte accumulation characteristic of NOD/Lt. Similarly, NOR/Lt peritoneal macrophages exhibited depressed interleukin-1 secretion characteristic of NOD/Lt. In addition to their diabetes resistance, NOR/Lt mice were distinguished from NOD/Lt by exhibiting more robust suppressor T-lymphocyte function. Outcross of NOR/Lt with NOD/Lt to generate heterozygosity at those chromosomal segments, defined by C57BL/KsJ markers in NOR/Lt parentals, did not produce insulitis or diabetes in F1 females. However, these F1 females were sensitive to cyclophosphamide-induced diabetes. In summary, the NOR/Lt strain is an MHC-matched diabetes-resistant control strain for NOD/Lt. Moreover, NOR/Lt will help identify the location and function of a non-MHC gene or genes capable of conferring resistance against insulitis and diabetes.

In C3H mice, a major component of susceptibility to the diabetogenic action of an obesity mutation (diabetes, db) is male gender associated. We tested whether increased male susceptibility was an androgen receptor mediated process. C3H.SW/Lt-derived db/db males were rendered androgen-receptor function-deficient by introducing the testicular feminization (Tfm) mutation of the X-linked androgen receptor gene. The db/db Tfm/Y males (phenotypically female in appearance) developed severe diabetes indistinguishable from that observed in standard db/db X + Y males. Castration of standard C3H.SW/Lt-db/db males (producing mutants with normal androgen receptors but reduced serum testosterone) also failed to block the gender-enhanced susceptibility. In contrast, female db/db littermates exhibited a milder hyperglycemia, and were more resistant to pancreatic beta cell necrosis and islet atrophy than any of the groups of db/db males. Although these data indicated that male-enhanced sensitivity to diabetogenic stress was independent of circulating androgens, the possibility that the gender dimorphism is predicated upon tissue ratios of active estrogens to androgens in glucose-producing tissues such as liver is discussed.

Genetic outcross and backcross analysis of nonobese diabetic (NOD/Lt) mice with a related but diabetes-resistant strain, nonobese normal (NON/Lt), has demonstrated that susceptibility to insulin-dependent diabetes mellitus is controlled in a recessive fashion by multiple genetic loci, including one (Idd-1s) associated with H-2 on chromosome 17 and another (Idd-2s) associated with Thy-1b/Apoa-1b (formerly Alp-1) on chromosome 9. To analyze the separate pathogenic contributions of Idd-1s and Idd-2s, two distinct congenic stocks of NOD/Lt mice homozygous on chromosomes 17 and 9 for NON/Lt linkage markers for the respective resistance alleles (Idd-1r and Idd-2r) were developed. The recessive nature of Idd-1s was confirmed at the fifth backcross generation in that 83% of females and 29% of males homozygous for NOD H-2 haplotype developed diabetes, whereas no diabetes occurred in any of the mice homozygous or heterozygous for the NON haplotype. However, codominant and recessive MHC-associated susceptibility genes in this congenic stock were indicated by the finding that at least one copy of the NOD/Lt MHC was required for insulitis development. Virtually no insulitis was detected in the pancreases of mice homozygous for NON haplotype at 42 wk of age, whereas heavy generalized insulitis was present in 3 of 19 H-2 heterozygotes and in 7 of 7 diabetic and 3 of 5 nondiabetic mice homozygous for NOD haplotype. Further indication of the presence of MHC-associated codominant and recessive MHC-associated susceptibility genes was the observation that the NOD MHC haplotype correlated in a codominant fashion with a relative increase in the percentage of splenic T-lymphocytes bearing the Ly-2 surface marker. Severe insulitis and concomitant high diabetes incidences occurred in all genotypic classes of congenic mice carrying Thy-1/Apoa-1 linkage markers for either NOD or NON alleles at Idd-2. Molecular analysis indicated that the NON-derived Idd-2r resistance allele had been replaced by recombination with Idd-2s from NOD. Restriction-fragment-length polymorphism analysis of two polymorphic markers proximal to Thy-1, low-density lipoprotein receptor Ldlr and Ets-1, a protooncogene, confirmed a recombinant chromosome 9, because homozygosity for NOD genomic fragments was found centromeric to an NON congenic segment of at least 20 centiMorgans spanning the Thy-1 and Mod-1 loci.(ABSTRACT TRUNCATED AT 400 WORDS)

A mutation in the BALB/cHeA subline of mice has resulted in loss of the glycerol-3-phosphate dehydrogenase (glycerol-P dehydrogenase) activity in adult tissues. Analysis of F2 offspring segregating for enzyme activity levels and a PvuII restriction fragment length polymorphism in the Gdc-1 gene on Chromosome 15 indicates that the mutation has occurred in or around the structural gene. Southern blot analysis failed to detect any major change due to chromosomal insertion, deletion, or rearrangement of the mutant gene. In vitro measurements of transcription in isolated nuclei failed to detect any difference in transcription between the BALB/cHeA and BALB/cBy strains of mice. However, Northern blot analysis with poly(A+) RNA isolated from brown fat shows that the mutant has about a 50-fold reduction in hybridizable transcripts of altered size. The data suggest that the mutation affected the processing of nuclear transcripts of glycerol-P dehydrogenase. The morphological, physiological, and reproductive characteristics of the mutant mice appear normal. This suggests that alternate pathways of energy metabolism and lipid synthesis exist which obviate the function of glycerol-P dehydrogenase.

BALB/cJ male mice were resistant and BALB/cByJ males were susceptible to induction of diabetes by multi-dose streptozotocin (MSz). Although both closely-related BALB/c substrains expressed H-2d haplotype, they could be differentiated by allelic differences at three genetic loci [Qa-2 (Chr 17), Bcd-1 (Chr 5), and Afr-1]. (BALB/cJ X BALB/cByJ)F1 males inherited the BALB/cJ resistance phenotype in a dominant fashion, thereby eliminating the BALB/cJ-expressed Afr-1b (recessive) allele as the susceptibility locus. Backcross of F1 mice to the susceptible BALB/cByJ strain produced a 1:1 segregation of susceptible and resistant (F1-like) phenotypes, suggesting that susceptibility was controlled by a single recessive gene. No linkage was found between the putative susceptibility gene and the mutant BALB/cByJ Qa-2,3 gene linked to the H-2 complex or with the mutant Bcd-1c allele. Since the resistant F1 males expressed low levels of androgen-dependent mouse urinary protein characteristic of the resistant BALB/cJ parental strain, the possibility was discussed that the alleles controlling sensitivity to MSz also controlled tissue sensitivity to endogenous androgens. An environmental effect on phenotype expression was indicated when BALB/cByJ males obtained from a colony free of pneumonia virus of mice (PVM) showed an attenuated rate of response to hyperglycemia induction in comparison to males obtained previously from an enzootically infected colony.

Interferons (IFNs) induce in responsive cells the synthesis of various proteins including a set with high binding affinities to guanylates. These guanylate-binding proteins (GBPs) were analyzed in cells from 46 inbred mouse strains using GMP-agarose affinity chromatography. In cells of 11 strains, including A/J, BALB/cJ, and C3H/HeJ, type I and II IFNs induced the synthesis of a major GBP of Mr 65,000, designated here GBP-1, and of at least three minor GBPs. In contrast, cells of the remaining 35 strains, including DBA/2J, C57BL/6J, and A2G, failed to synthesize GBP-1 in response to both types of IFNs. Induction of the minor GBPs was comparable in cells of both groups of mice, confirming that they were all responsive to IFNs. Analysis of F1, F2, and BC1 offspring of crosses between GBP-1 inducible (A/J) and noninducible (DBA/2J or A2G) strains showed that inducibility of GBP-1 was inherited as a single autosomal gene. The symbol Gbp-1 is proposed for this locus, designated Gbp-1a for the allele causing inducibility and Gbp-1b for the other allele.

Somatic cell hybrids, recombinant inbred (RI) mouse strains, and backcross breeding experiments were used to locate the gene of transcobalamin II (Tcn-2), the vitamin B12 binding protein in mouse serum. TCN-2 was found to be useful genetic marker in the somatic cell hybrids. Selected hybrid clones were derived from fusions between GR mouse cells and the Chinese hamster cell line E36. Analysis of mouse specific chromosomal enzyme markers in relationship to TCN-2 secretion, in the hybrid clones, provided provisional evidence for assignment of the Tcn-2 locus to chromosome 11. The strain distribution pattern of the TCN-2 variants S and F in the RI series CXS, constructed from the cross of BALB/cHeA (TCN-2S) with STS/A (TCN-2F), implied a close linkage with the hemoglobin alpha-chain locus (Hba) on chromosome 11. Backcross breeding using inbred strains confirmed these findings and located the Tcn-2 gene closest to the centromere, linked with waved 2 (wa-2) and Hba with recombination frequencies of 6.9 and 19.2% each. The linkage group Tcn-2/wa-2/Hba was established.

We describe genetic, haematological and biochemical properties of a new mouse pigment mutant, cocoa (coa). Cocoa is a recessive mutation located on the centromeric end of chromosome 3 near the Car-2 locus. The mutation causes increased bleeding time accompanied by symptoms of platelet storage pool deficiency (SPD), including decreased platelet serotonin and decreased visibility of dense granules as analysed by electron microscopy of unfixed platelets. Dense granules were visible in normal numbers when platelets were incubated with the fluorescent dye, mepacrine. The intragranular environment, however, was abnormal as indicated by decreased flashing of mepacrine-loaded dense granules after exposure to ultraviolet light. Unlike the previously described seven mouse pigment mutations with SPD in which pigment granules, platelet dense granules and lysosomes are affected, the cocoa mutant had normal secretion of lysosomal enzymes from kidney proximal tubule cells and platelets. The cocoa mutation thus represents an example of a single gene which simultaneously affects melanosomes and platelet dense granules but probably does not affect lysosomes. The results indicate that melanosomes and platelet dense granules share steps in synthesis and/or processing. Cocoa may be a model for cases of human Hermansky-Pudlak syndrome in which functions of melanosomes and platelet dense granules, but not lysosomes, are involved.

A metabolic screening program of inbred strains of mice has detected a marked organic aciduria in the BALB/cByJ strain. Gas chromatographic and mass spectrometric analysis identified large quantities of n-butyrylglycine plus lesser quantities of ethylmalonic acid. Crosses with the nonexcreting C57BL/6J strain indicate that this condition is inherited as an autosomal recessive trait. Independently from this screening a variant with no detectable enzyme activity of butyryl CoA dehydrogenase (BCD) in liver and kidney of the BALB/cByJ strain but not other BALB/c sublines was discovered. Data from a three-point cross indicated that the null variant maps to the structural locus for the enzyme, Bcd-1, on chromosome 5. The findings indicate that a mutation at or near Bcd-1 in the BALB/cByJ strain resulted in a biochemical abnormality manifest as the BCD deficiency. It is concluded that accumulation of butyryl CoA due to a block in the oxidation of short-chain fatty acids results in an overproduction of organic metabolites leading to the observed organic aciduria. The fact that other BALB/c substrains do not exhibit this abnormality further suggests that this disorder reflects subline divergence within the BALB/c family.

The pathogenesis of diabetes in C57BL/KsJ-db/db mice has been proposed to entail autoimmune mechanisms. We have combined immunodeficiency genes with the db mutation to determine whether beta cell necrosis and establishment of severe diabetes would occur in the absence of normal T and/or B lymphocyte functions. Inbred mice carrying the recessive mutations, severe combined immunodeficiency (scid), X-linked immunodeficiency (xid), nude (nu), and the Y-linked autoimmune accelerator (Yaa), were crossed with strains congenic for the db mutation. The diabetes syndrome was studied in double homozygotes produced in the F2 generation. In another experiment, C57BL/KsJ-db/db males were made T cell function deficient by adolescent thymectomy followed by lethal irradiation and bone marrow reconstitution. None of these manipulations served to prevent the induction of a severe diabetes syndrome in any of the model systems analyzed. Thus, diabetogenesis characterized by massive necrosis of the pancreatic beta cells and atrophy of the pancreatic islets was observed in both the absence of normal T cell function (as assessed by absence of T cell mitogen response) and humoral autoimmunity against beta cell antigens (insulin, retroviral p73). In conclusion, our data indicate that anti-beta cell autoimmunity is not a primary event in the etiopathogenesis of diabetes in the db/db mouse.

Feeding 0.001% estrone in a diet to C57BL/KsJ mice homozygous for the recessive obesity gene "diabetes" (db) permitted dissociation of the primary consequences of obesity gene expression from the secondary consequences of diabetes effected through interaction between the db gene and other diabetogenic genes in the inbred background. Estrone-treated db/db mice were similar to untreated mutants in exhibiting hyperphagia and marked obesity. However, estrone-treated mutants did not develop the hyperinsulinemia, hyperglycemia, and islet atrophy characteristic of untreated db/db mice. Thus, expression of the primary defect could be studied in the absence of the myriad secondary sequelae elicited by chronic hyperinsulinemia and hyperglycemia. Reduced numbers of hepatocyte plasma membrane insulin receptors (50% of normal) persisted in the estrone-treated mice in the absence of hyperinsulinemia, indicating that this deficiency was a consequence of the primary genetic defect and not merely a downregulation phenomenon secondary to hyperinsulinemia. Comparison of insulin secretion from comparably sized +/+ islets versus islets from estrone-treated db/db mice showed no intrinsic defects in beta-cell sensitivity to glucose. In conclusion, db-induced obesity can be dissociated from hyperinsulinemia, hyperglycemia, beta-cell dysfunction, and hyperphagia but is associated with a generalized membrane defect reflected in part by the persistent deficiency of plasma membrane insulin receptors.

A polygenic basis for susceptibility to insulin-dependent diabetes in nonobese diabetic (NOD) mice has been established by outcross to a related inbred strain, nonobese normal (NON). Analysis of first and second backcross progeny has shown that at least three recessive genes are required for development of overt diabetes. One, Idd-1s, is tightly linked to the H-2K locus on chromosome 17; another, Idd-2s, is localized proximal to the Thy-1/Alp-1 cluster on chromosome 9. Segregation of a third, Idd-3s, could be shown in a second backcross. Neither Idd-1s nor Idd-2s could individually be identified as the locus controlling insulitis; leukocytic infiltrates in pancreas were common in most asymptomatic BC1 mice. Both F1 and BC1 mice exhibited the unusually high percentage of splenic T lymphocytes characteristic of NOD, suggesting dominant inheritance of this trait. The polygenic control of diabetogenesis in NOD mice, in which a recessive gene linked to the major histocompatibility complex is but one of several controlling loci, suggests that similar polygenic interactions underlie this type of diabetes in humans.

GBP-1 is the predominant species of a family of guanylate-binding proteins synthesized in mouse cells in response to interferons (IFNs) alpha, beta, or gamma. IFN inducibility of this 65,000-Da protein is controlled by alleles at a single autosomal locus, Gbp-1, with allele a encoding inducibility and allele b noninducibility. Here, we present evidence suggesting that both alleles occur in outbred populations of wild mice. Using recombinant inbred strains and classical linkage analysis of offspring of two-point and three-point backcrosses we demonstrate that Gbp-1 is linked to Adh-3 (encoding alcohol dehydrogenase C2) and VaJ (varitintwaddler-Jackson) located on the distal part of chromosome 3. The relevant recombination frequencies (RFs) (+/- SE) were 3.5 (+/- 1.1) and 11.7 (+/- 2.8)%, respectively. We further show that strain B6.C-H-23c/By(HW 53), congenic for a small segment of chromosome 3, carries the BALB/c alleles at both the Gbp-1 and the Adh-3 locus and not the alleles of the B6 background strain confirming the chromosomal location and close linkage of the two loci.

The effect of human recombinant interleukin-2 (IL-2) on the proliferative and cytotoxic response of peripheral blood mononuclear cells was analyzed in 12 severely injured patients. The in vitro proliferative response (measured from tritiated thymidine uptake) was normal during the first post-injury week, but rapidly decreased from the second week. The cytotoxic response to natural killer cell-resistant target T24 was likewise diminished from the second week. To clarify if the defect in cytotoxic response was due to numerical reduction of precursors or to reduced responsiveness, limiting dilution assay was introduced. No post-trauma reduction in precursor numbers was observed. These data collectively suggest that, in addition to impaired IL-2 production, there is an endogenous defect in IL-2 responsiveness. In the context of high incidence of septic complications, the observations may be clinically important.