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The present studies characterize at the clonal level the repertoire of lipopolysaccharide-responsive murine B lymphocytes committed to the production of antibodies reactive with denatured DNA. This repertoire is vast in normal mice as 1-5% of total mitogen-induced antibody-forming cell clones secreted denatured DNA-reactive antibodies when the splenocyte donors were CBA (Ighj), BALB/c (Igha), C57BL/6 (Ighb), CBA nu/nu, and C57BL/6 nu/nu athymic mice. The autoimmune NZB (Ighe) strain did not display elevated proportions of anti-denatured DNA antibody-forming cell precursors. Cross-reactions shown by CBA anti-denatured DNA antibodies suggest that many antibodies might derive significant binding energy from interaction with the bases or similar hydrophobic moieties. Cross-reactions with other tested polynucleotides were frequent, but cross-reactions with phospholipids and phosphocholine were undetectable. Most anti-DNA antibodies bound preferentially or exclusively to single-stranded denatured DNA as compared to double-stranded native DNA. The frequency of anti-denatured DNA antibody-forming cell precursors among CBA peritoneal cells was not elevated. Fluorescence-activated cell sorter-selected Ly-1-positive NZB splenic B cells were not enriched, and Ly-1 negative B cells were not depleted of anti-DNA antibody-forming cell precursors. These results show that antibody-forming cell precursors specific for denatured DNA are not restricted to the Ly-1 positive B-cell subset.

Two different cross-reactive idiotype (CRI) groups are distinguishable in the Ab response of A/J mice to the p-azobenzenearsonate (ABA) hapten: CRIA and CRIm. These two groups showed distinct patterns of relative dominance in the ensuing response depending on whether the inducing Ag was a T cell-dependent (TD) form of ABA, such as ABA-KLH or ABA-CGG, or a T-independent type 1 (TI-1) form, such as ABA-Brucella abortus or ABA-lipopolysaccharide (LPS), and on whether the response was elicited in vivo or in vitro. The CRI+ component of primary in vivo plaque-forming cell (PFC) responses to TD ABA Ags was largely (greater than 90%) CRIA+ as was, to a slightly lesser extent (greater than 75%) the CRI+ portion of secondary or hyperimmune serum Ab or PFC responses to the same Ags. In contrast, in vivo primary and hyperimmune PFC responses to ABA-Bru or ABA-LPS showed a significantly lower CRIA/CRI ratio, averaging 0.5-0.6, with some individual mice giving figures as low as 0.2, indicating predominance of CRIm over CRIA. Serological analysis of hyperimmune anti-ABA Abs from a group of 5 A/J mice immunized with ABA-Bru gave a figure of less than 0.5 for the CRIA/CRI ratio. The most striking disparity from the TD pattern was seen in primary in vitro PFC responses to the TI ABA Ags; here ratios of less than 0.2 were generally seen. Since T cell removal did not alter the Id pattern in the TI responses, CRIA-specific Ts cells do not account for the weak expression of CRIA in such responses. We propose a model that explains these results on the basis of differential expression of IdX dominance by two distinct B cell subpopulations--equatable to the Lyb-5+ and Lyb-5- B cell subsets--along with differential relative activation of these subsets in different types of responses. Examination of anti-ABA PFC responses of F1 progeny of CBA/N and A/J mice to ABA-Bru lends support to this hypothesis since CRIA expression was significantly lower in mice with the xid defect.

The requirement for idiotype-specific helper T (Th) cells in the generation of a major intrastrain crossreactive idiotype was investigated. This idiotype, designated CRIA, is associated with a large proportion of anti-p-azobenzenearsonate (anti-Ar) antibodies in A/J mice. Secondary in vitro responses were studied. Using carrier-primed heterogeneous Th-cell populations, it was found that CRIA expression is determined by the mouse strain that provides the responding B cells and is independent of the strain of the Th cells functioning in vitro. Thus, A/J or A.BY (Ighe) B-plus-accessory-cell populations, primed in vivo to keyhole limpet hemocyanin-Ar (KLH-Ar), generated CRIA-dominant responses in vitro in the presence of KLH-Ar regardless of whether the KLH-primed Th cells were derived from CRIA+ strains (A/J or A.BY, Ighe) or CRIA- strains (B10.A or C57BL/10, Ighb). Further, when major histocompatibility complex-restricted, KLH-specific Th-cell clones were used, the CRIA dominance of the Ar-specific responses was again determined by the strain providing B plus accessory cells. Similar levels of expression of CRIA in Ar-specific antibodies were generated in the presence of heterogeneous or cloned Th cells. The results suggest that there is no absolute requirement for idiotype-specific Th cells in generating an Ar-specific secondary antibody response in vitro.

1. Peritubular capillary microperfusion was used to examine the effects of protein-free and hyperoncotic homologous plasma on fluid reabsorption by proximal convoluted tubules in the hydropenic rat. 3H-labelled p-aminohippurate was added to perfusates for the purpose of estimating the extent to which tubules under study were bathed by the perfusates. [14C]Mannitol was added to perfusates in order to detect contamination of collected tubular fluid by perfusates. 2. Hydrostatic pressures were monitored in the peritubular microvasculature and adjacent proximal tubules during perfusion. Evidence for secretion of p-aminohippurate from perfusate into tubules under study was determined by collecting tubular fluid from both early and late puncture sites. Fractional and absolute reabsorption were not affected by either the protein-free or the hyperoncotic plasma. 3. When acetazolamide was added to the perfusate both fractional and absolute reabsorptive rates decreased by an average of 36%, indicating that the techniques were capable of detecting a decrease in proximal tubular reabsorption. 4. It is concluded that under the conditions of this study changes in peritubular capillary protein concentrations have no detectable effect on the rate of proximal convoluted tubule fluid reabsorption.

We report on the preparation, crystallization, and preliminary x-ray crystallographic study of Fab fragments from monoclonal anti-p-azophenylarsonate antibodies. Several crystalline forms were obtained with the Fab fragment from the R19.9 monoclonal antibody as well as with the complex between the hapten p-aminobenzenearsonic acid and Fab R19.9. The crystals of this hapten-Fab complex are similar to but not always isomorphous with the native Fab crystals. All the native and complex crystals were obtained using polyethylene glycol 6000 as crystallizing agent. Some of these crystalline forms diffract to a 2-A resolution or beyond and are suitable for high resolution x-ray diffraction analysis. A possible interpretation of hapten binding to crystalline Fab fragments from R19.9 and from the R9.3 monoclonal anti-p-azophenylarsonate antibody, implying conformational changes, is discussed.

In Experiment 1, data from 129 Duroc and Hampshire boars, barrows and gilts were used to develop a more rapid and much less expensive method of estimating longissimusmuscle area in the live pig. The method involved ultrasonic measurement of the muscle depth at a point 6.4 cm from the dorsal mid-line and perpendicular to the skin at that point. Each centimeter of muscle depth approximated 1 in.2of muscle area. Measurements of muscle depth from tracings of the muscle in the carcass were highly correlated (r=0.91) with actual muscle area at the 10th rib. The correlations of muscle depth with ham and loin percent (r=0.57) and lean cuts percent (r=0.56) were comparable to those between loin eye area and these two cutout measures (r=0.59). The method was tested on 74 pigs in Experiment 2. Ultrasonic estimates of longissimusdepth in the live pigs showed correlations with actual area in the carcass at the 10th rib (r=0.67) and at the last rib (r=0.74) which are comparable to those found by other researchers using more elaborate equipment and/or more expensive techniques.