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A hypothesis is proposed that multiple "LOGIC" genes control Boolean logic in a neuron. Each hypothetical LOGIC gene encodes a transcription factor that regulates another LOGIC gene(s). Through transcription regulation, LOGIC genes connect into a complex circuit, such as a XOR logic gate or a two-input flip-flop logic circuit capable of retaining information. LOGIC gene duplication, mutation and recombination may result in the diversification of Boolean logic gates. Creative thinking may sometimes require counter-intuitive reasoning, rather than common sense. Such reasoning is likely to engage novel logic circuits produced by LOGIC somatic mutations. An individual's logic maturates by a mechanism of somatic hypermutation, gene conversion and recombination of LOGIC genes in precursor cells followed by selection of neurons in the brain for functional competence. In this model, a single neuron among billions in the brain may contain a unique logic circuit being the key to a hard intellectual problem. The output of a logic neuron is likely to be a neurotransmitter. This neuron is connected to other neurons in the spiking neural network. The LOGIC gene hypothesis is testable by molecular techniques. Understanding mechanisms of authentic human ingenuity may help to invent digital systems capable of creative thinking.

Tumor escape from the host immune response remains the major problem holding the development of immunotherapies for cancer. In this review, congenic mouse lines are discussed that differ dramatically in their ability to respond to tumors tested and, thereby, to survive or to succumb to the tumor and/or its metastases. This ability is under the control of either MHC class I or nontrivial MHC class II beta genes expressed in a small subpopulation of antigen-presenting cells. Two hypotheses can explain the results obtained so far: (1) emergence of tumor cell variants that escape the host immune response in morbid mice but are eliminated in survivors, and (2) tumor-induced immunosuppression, which is either efficient or not, depending on the congenic line used. It is argued that further experimentation on these congenics will allow to choose the correct hypothesis, and to characterize the mechanism(s) of elimination of minimal residual disease and prevention of tumor escape by the immune system of survivors as well as the reason(s) for its failure in morbid mice. It is also argued that the use of these models will substantially increase the chance to resolve the controversy of poor correlation of immunotherapy testing in mice with clinical results.

Novel single exon genes Abeta4-7 comprising the Abeta6 gene family have been cloned from mouse mutants surviving transplantable metastatic tumors. Their protein coding sequences are similar to H2-Ab cDNA which encodes antigen-binding molecules of antigen presenting cells (APC); their promoters and/or signal sequences are unrelated to Ab sequences but found in other eukaryotic genes. Abeta4(b) protein was demonstrated on macrophages and B cells that are APC. The Abeta6(w302) appears to be an ancient gene ancestral to major histocompatibility complex (MHC) class II beta genes. However, unlike the MHC class II, the Abeta4-7 genes are not involved in skin graft rejection. Despite inbreeding, the Abeta6(w302) locus remains unfixed in several strains of mice. The number of Abeta genes and their alleles varied between individual mice; they do not map into the H2 region but appear to be scattered over the genome. The Abeta6 gene family is molecularly unstable in Abeta6(w302)-positive (but not in Abeta6(w302)-negative) mice which are somatic mosaics for these genes. Biological features of Abeta4-7 genes make them remarkably different from the classical MHC gene system. All available evidence strongly suggests that these genes control susceptibility/resistance to the spread of metastatic tumors.

Metastatic tumors escape from immune response and spread in the body; survivors are very rare. Novel single exon genes A beta 4-7 and a pseudogene A beta 8 psi have been cloned from survivors. Their protein coding sequences are similar to MHC class II beta H2-Ab cDNA while their promoter is different from MHC promoters. The A beta 4 protein was demonstrated on macrophages (antigen presenting cells). The A beta gene family is genetically unstable in germ line and somatic cells of survivors. Mutants S-27 and S-87/1 lost the A beta 5s5 and acquired the A beta 6w302 gene; the Ab gene mutated in S-27. The proposed mechanism of resistance is molecular instability of the A beta gene family resulting in somatic mutations and wandering immune responses that destroy the tumor in the survivor.

Todja is a secluded region of northern Tuva-situated in the Sayany Mountains, Siberia. The aboriginal population of Todja is Tuvan. A total of 128 healthy Tuvans living in Todja were typed for HLA-A, -B and -C antigens and several plasma and erythrocyte protein polymorphisms (Hp, Tf, Gc, ESD, ACP, PGM1, PGD and ADA). The observed frequencies of all 8 blood protein and HLA genotypes were in agreement with Hardy-Weinberg expectations. The most frequent HLA antigens in Todjans are A2 (0.36), A3 (0.24), A9 (0.50), B15 (0.34) and B40 (0.50). HLA haplotypes A2B5, A2B40, A9B15 and A9B40 are most common in this population. The observed frequencies of protein polymorphisms and HLA antigens and haplotypes in Todjans are similar to those of other Mongoloid populations. A comparison of HLA frequencies currently observed in Todjans with those obtained 20 years ago at the same locality showed minor changes attributable to the effect of migration.

The paper presents some experimental data and speculations about antituberculous resistance and immunity in mouse mutants resisting spread of transplantable syngeneic tumor.

In this review, new data are interpreted that provide some answers to the question of why the immune system fails to respond to metastatic cancers. A function such as an element of the immune response is expected to be under the control of a gene. To find a gene, a mutant is required. Complex screens have been designed and used to detect mouse mutants resisting spread of transplantable tumors (in a spontaneous metastasis assay). Curiously, both mutants with increased and decreased resistance to spread of the tumor have been found. S-27 is a strongly resistant mutant linked to MHC; this mutation also affected some responses to Mycobacterium tuberculosis infection. A long sought link between malignant transformation and vaccination against mycobacterial diseases is discovered in this mutant. A search for a molecule responsible for effects of the S-27 mutation resulted in an unexpected finding. The S-27 mutant carries complex nucleotide alterations at the junction between the signal sequence and the sequences coding for the mature MHC class II A beta polypeptide chain. Antigen recognition region of the A beta molecule is not affected by this mutation. Some concepts developed during the course of this study are illustrated in Figures 1 to 4.

To search for host genes for resistance/susceptibility to cancer metastasis, mutation analysis was employed. Ten putative mutants of resistance to lymphoma EL4 and four putative mutants of resistance to sarcoma MCA/77-23 of C57BL/6J (B6) mice were produced. These mutants were designated S (for "survivor") mutants; they do not reject parental strain B6 skin grafts. S-mutants resist moderate tumor cell doses: TD50 values in them were increased by a factor of 12 to 600. Genetic linkage tests showed that five S-mutants were linked to mouse major histocompatibility complex (H-2) and five other S-mutants were not linked to this locus. A group of H-2-linked S-mutants resisting EL4 and a mutant, S-87/2, resisting MCA/77-23 were tested for resistance to spontaneous metastases of the same two tumors, EL4 and MCA/77-23. Two of the mutants, S-31 (lymphoma-resisting) and S-87/2 (sarcoma-resisting), were shown to carry mutations of mouse gene(s) for resistance to tumor metastases. In both of these mutants resistance to the original tumor transplant coexisted with highly increased susceptibility to metastasis. These mutants are a new tool to study genes for resistance to cancer metastasis and of mechanism of resistance controlled by each individual gene.

"S" (survivor) mutants were produced in mice for genetic analysis of host resistance to metastatic cancers. S-mutants S-27 and S-31 resist transplantation of lymphoma EL4 of parental C57BL/6J (B6) mice while they accept parental skin grafts. Mutant S-27 also resists formation of spontaneous metastases from intradermally growing EL4 tumor into lymph nodes; mutant S-31 is highly susceptible to EL4 metastases. Another mutant, H-2bm26 (bm26), resists EL4 and rejects B6 skin grafts. Major histocompatibility complex (MHC) class I and class II gene expression was compared in these mutants and normal B6 mice. All three mutants tested, S-27, S-31, and bm26, expressed a low amount of Kb mRNA in organ-specific fashion. Mutants bm26 and S-31 expressed a low amount of Abb mRNA and of Ab antigen on their spleen cells. Some oligonucleotide probes designed to hybridize to the second exon of the class II MHC gene Abb did not hybridize with DNA from all three mutants. These findings suggest extensive sequence alterations in the Abb gene in mutants S-27, S-31, and bm26; they also suggest a major role of MHC in the control of host resistance to spontaneous metastases of the EL4 tumor.

Mutation M523 (H-2ka) occurred spontaneously in strain CBA/CaLacSto and was discovered during routine skin graft testing for genetic homogeneity. By linkage and complementation tests, the mutation was previously mapped in the K end of the H-2 complex. We demonstrate that the mutation occurred in the K region, without affecting the I region in the K end of the complex. The mutant antigens cause rejection of skin grafts, stimulate cells in mixed lymphocyte culture, and function as stimulators as well as targets in cell-mediated lymphocytotoxicity. Yet, they are serologically indistinguishable from the antigens of the original strain and do not induce formation of humoral antibodies upon immunization of the CBA strain. Together with the results obtained on testing of other H-2 mutants, the data strongly support the notion that classical H-2 antigens (i.e., products of the H-2K and H-2D loci) can function as lymphocyte-stimulating determinants, and that I-region differences are not required for the induction of strong cell-mediated lymphocytotoxicity.

The magnitude of the cytotoxic effect (CE) of immune lymphocytes R101 anti-Kb (C57BL/6) and R101 anti-Dd (B10.D2) upon target cells (TC) of mutants Kba (Hzl) and Kbd (M505), as well as Dda (M504) was considerably less than that on the TC of the original C57BL/6 and B10.D2 strains, respectively. A decrease of the CE on the H (zl) and M504 TC was more prominent than that on the M505 TC. "Monospecific" lymphocytes anti-Kb and anti-Dd were separated into two distinct subpopulations by absorption on the monolayers of macrophages from the mutant strains of mice. One of the subpopulations reacted with the TC of the original strain only, whereas the other one - with the TC of both the original and mutant strains.

The distribution of HLA phenotypes, gene and haplotype frequencies was studied in three Mongoloid populations in Central Asia (Tofs, Tuvinians and Buryats). In comparison with Caucasian populations increased frequency of HLA-A9, BW40 and BW15 and haplotype A9, BW15 as well as low frequency of HLA-A1, B8 and B12 are characteristic of all three populations. Buryats seem to have the relatively highest admixture of Caucasoid genes.

Two mechanisms of major histocompatibility complex (MHC) mutations have been described in mice; gene conversion and homologous but unequal recombination. However, our knowledge of mutations in MHC is incomplete because studies have been limited almost exclusively to two haplotypes, H-2b and H-2d, while hundreds of haplotypes exist in nature; it has been biased by the use of only one procedure of screening for mutation, skin grafting. We used three procedures to screen for MHC mutations: (1) conventional techniques of skin grafting, (2) syngeneic tumor transplantation and (3) typing with monoclonal anti-MHC antibodies (mAbs) and complement. The faster technique of tumor transplantation detected mutants similar to those discovered by skin grafting technique. Screening with mAbs allowed us to detect both mutants that are capable of rejecting standard skin grafts and those that are silent in skin grafting tests, and which therefore resulted in a higher apparent mutation frequency. Two mutants of the H-2a haplotype were found that carry concomitant class I and class II antigenic alterations. Both MHC mutants silent in skin grafting tests and mutants carrying concomitant class I and class II alterations have never been studied before and are expected to reveal new mechanisms of generating MHC mutations. 1-Ethyl-1-nitrosourea (ENU) failed to induce de novo MHC mutations in male mice in our skin grafting series.

Recent experiments have shown that different regions of myelin basic protein (MBP) are encephalitogenic for different inbred strains of mice. It was therefore of interest to determine whether the immune response to MBP was MHC associated, and if so, what subregion controlled this response. Because PL/J and A/J mice were good responders to mouse MBP and C57Bl/10SN were not, B10.PL(73NS) and B10.A mice were immunized with mouse MBP under conditions designed to induce EAE. These strains were found to be highly susceptible. Intra-H-2 recombinant mice were then assessed for susceptibility. B10.A(4R) and B10.MBR were susceptible, whereas B10.A(5R) were resistant. Thus, EAE induced by purified MBP is under the control of the MHC, and the response maps to the I-A subregion. Production of IL 2 in vitro by T cells from MBP-primed mice in the presence of antigen and adherent cells was blocked by monoclonal antibody to the I-A, but not the I-E, subregion. When the specificity of the encephalitogenic response was tested, peptide 1-37 was active in B10.PL(73NS) and B10.A mice, whereas peptide 89-169 was active in A.SW, SWR, and B10.T(6R) strains. Serum from mice immunized with MBP peptides was assayed for antibody content. PL, B10.PL, and B10.A mice made a good antibody response to peptides 1-37 and 43-88 but were nonresponsive to peptide 89-169. SJL, A.SW, SWR, and B10.T(6R) mice responded well to peptide 89-169 but were poorly responsive to peptides 1-37 and 43-88.

The differences in the H-2 system between mice of the C57BL/10 (H-2b) and 129 (H-2bc) were studied in crosses B10.D (H-2d) or recombinant strains R106 (KbSbDda), R107 (KbSbDd) and R101 (KdSdDb) with strains 129 or B10.129 (6M). Most skin grafts from the strain C57BL/10 were rapidly rejected in the F1 hybrids derived from the crosses with strains B10.D2, R106 and R107, thus indicating to the effect of the relatively strong H-locus either in the D region or in the Tla region of H-2b. Chronic responses were observed in the F1 hybrids derived from crosses with the strains R101 and R103, indicating to the weak effect of another locus. However all the skin grafts survived in the F1 hybrids with the strain HTG (KdSdDb). This weak H gene is apparently located to the left of the crossover in the recombinants R101 and R103, but to the right of the crossover in the HTG, i. e. between the loci Slp and H-2D. The new locus is tentatively designated as H-2W.

In this study, data are presented on serologic H-2 typing of 320 wild mice collected in several parts of Europe and Egypt. The sample was typed for 39 class I (K, D) and 16 class II (Ia) antigens. The phenotype frequencies of class I and class II antigens showed high variability in their distribution among different areas, ranging from absence or presence in low frequency in one area to presence in about one-half of the mice in another area. The average phenotypic frequency of class I private antigens was 6.3%; at least 60% of class I alleles (blanks) could not be identified with the available reagents. The data suggest that there might be more than 100 alleles for each class I locus, H-2K and H-2D. The average phenotypic frequencies of Ia-1 private antigens was 10.8%. About 75% of Ia-1 alleles (blanks) could not be identified. The number of Ia-1 alleles was estimated to be in the range of 20 to 50.

Receptors of effector T lymphocytes of congeneic strains of mice do not recognize public H-2 specificities and react to private H-2 specificities only. This has been established with the use of three tests: direct cytotoxicity assay of immune lymphocytes upon target cells, specific absorption of the lymphocytes on the target cells, and rejection of skin grafts at an accelerated fashion. Immunization with two private H-2 specificities in the system C57BL/10ScSn leads to B10.D2 induces formation of two corresponding populations of effector lymphocytes in unequal proportion: a greater part of them is directed against the private specificity H-2.33 (Kb), while the smaller part is towards H-2.2 (Db) private specificity. These two populations of effector lymphocytes do not overlap, as demonstrated by experiments on their cross-absorption on B10.D2 (R107), B10.D2 (R101), B10.A(2R), and B10.A(5R) target cells, as well as on mixtures of R107 and R101 targets. Following removal of lymphocytes reacting with one of the private H-2 specificities, lymphocytes specific to the other specificity are fully maintained. A mixture of target cells, each bearing one of the two immunizing private specificities, absorbs 100% of the immune lymphocytes and is totally destroyed by them. It is suggested that H-2 antigens are natural complexes of hapten-carrier type, in which the role of hapten is played by public H-2 specifities and that of the carrier determinant by either private H-2 specificities or structures closely linked to them. Various models of steric arrangement of MHC determinants recognized by receptors of effector T lymphocytes are discussed.

Three mutants of the H-2K gene within the mouse major histocompatibility complex were studied. Antisera anti-H-2.5 + 39 were unable to agglutinate H-2ba and H-2bf mutant red blood cells. The same sera moderately agglutinated H-2b red blood cells. The H-2ba red blood cells did not absorb in vitro the activity from an anti-H-2.5 serum, while the H-2b cells did. Thus, these results indicate the existence of qualitative SD antigenic differences among H-2Kb derived mutants. In the proliferative graft versus host test the H-2ba spleen cells did not induce spleen enlargement in the H-2bd recipients, while pronounced reaction was recovered in bd-ba combination. The (baXb) F1 hybrid cells were as efficient as b/b homozygous cells. The data suggest that the H-2K gene product may be involved in the antigen recognition process by T cells.

H-2fa is a spontaneous mutation that occurred in an (A.CA X A)F1 female mouse and was later transferred on an A-strain background [congenic line A.CA (M506) or M506]. Skin grafts exchanged between M506 and A.CA strains are rejected within 4 weeks after grafting. Significant reaction is observed when these two strains are used as responders and stimulators in mixed lymphocyte culture or in a splenomegaly graft-versus-host assay. The mutant antigen induces strong cell-mediated lymphocytotoxicity. The mutation maps in the K end of the H-2 complex. The capacity of mutant antigens to induce relatively strong lymphocyte proliferation is explained by hypothesizing that the T-cell receptors reacting with K- or D-region products can more easily recognize subtle than drastic alloantigenic differences.

H-2 mutant/normal pairs of congenic mouse strains C57BL/6equilibriumB6.M505 (H-2Kbd), C57BL/6equilibriumB6.C(Hz1) (H-2Kba) and A.CAequilibriumA.CA(M506) (H-2fa) were studied in the graft versus host assay. All the three mutations were expressed in these tests as gain and loss of H-2 antigen. The data obtained confirm an earlier suggestion that the H-2K antigenic molecule bears antigenic determinants which could be detected by a variety of immunological techniques.

Inducibility of antinuclear antibodies (ANA) by mercuric chloride (HgCl2) was studied in various strains of mice. High response to the treatment was observed in strains A.SW (H-2s), A.CA (H-2f), A.TH (H-2t2), B10.S (H-2s), DBA/1J (H-2q), and P/J (H-2p); strains A.BY (H-2b), B10.M (H-2f), and C3H/HeSnJ (H-2k) showed a low response, while strains A/WySn (H-2a), A/J (H-2a), A.TL (H-2tl), BALB/cJ (H-2d), C57BL/10SnJ (H-2b), B10.A (H-2a), and PL/J (H-2u) did not produce any detectable ANA. Thus, the H-2a haplotype determines resistance to the treatment regardless of the genetic background; the H-2s determines susceptibility, while the H-2b and H-2f are intermediate haplotypes whose effect depends on the interaction with the background genes. Our results with intra-H-2 recombinant strains indicate that the I region of the H-2 complex is the major genetic factor controlling this response. The function of the I region is to control cellular cooperation in the immune response that finally results in production of antibodies specific for a particular antigen. Therefore, we postulated that the I region controls the antibody response to a nuclear antigen released as a result of HgCl2 toxicity in mice. A genetic study of an A.SW X C57BL/10 cross confirmed this observation, showing that resistance to ANA induction by HgCl2 in this strain combination is determined by interaction of a semidominant H-2-linked gene and one or more unlinked genes. The two drugs tested, gold sodium thiomalate and D-penicillamine, also induced ANA in A.SW mice, while other strains tested resisted this treatment.

Genetic polymorphism in the H-2:Qa:Tla region of chromosome 17 is associated with constitutive variation of bodily odor phenotypes which permit individual olfactory recognition among mice. To determine whether known genes in the H-2:Qa:Tla complex are concerned in the constitution of odor phenotypes, mice were tested for their ability to sense a difference between the B6/By (H-2b) and congeneic B6.C-H-2bm1 strains, which differ genetically by mutation of the H-2K gene. As in previous studies of the sensory discrimination of H-2:Qa:Tla phenotypes, mice were trained by reward in a Y maze to distinguish the odors of urine samples, and the successful distinctions of B6/By from B6.C-H-2bm1 were confirmed by transfer of training, without reward, to coded samples of urine from genetically equivalent urine donor mice which the trained mice had not previously encountered. Cosegregation of odor phenotype with H-2b and H-2bm1 was demonstrated by transfer of training to typed H-2b and H-2bm1 homozygous segregants of F2 generations of appropriate crosses. Although it is not excluded that the differences in odor phenotype which distinguish H-2b and H-2bm1 mice are directly related to the structure of the H-2b and H-2bm1 products, it is equally possible that H-2-related odor phenotypes arise from effects of H-2 genetic variation on metabolic pathways either directly, or indirectly through developmental polymorphism.