Immunization of NZB and A/J mice against an anti-DNA hybridoma antibody (F227) derived from (NZB x NZW)F1 (B/W) mice allowed the preparation of two anti-idiotypic antisera. These two reagents were shown to recognize different idiotopes of the F227 monoclonal antibody. NZB anti-idiotypic antibodies recognized non-ligand-modifiable idiotypic determinants. These idiotopes were private or present at undetectable level in BW mouse sera since it was found that only two of the 24 B/W mouse sera tested were recognized by these antibodies. Conversely, A/J anti-idiotypic antibodies recognized partially ligand-modifiable idiotopes which were found in all B/W mouse sera tested. These results demonstrate that anti-DNA antibodies share similar idiotypic specificities and suggest that these autoantibodies occur as families of structurally related proteins.

Recently, we reported evidence for the existence of an immunoglobulin X light chain (Ax) whose variable region differs from those encoded by the known Vk gene

The cellular localization of the vitamin D-dependent calcium-binding protein (CaBP) in the duodenum of rat was studied using indirect immunofluorescence and immunoperoxidase-staining methods. Specific positive reaction product, indicative of the presence of CaBP, was exclusively located within the villous part of the duodenal mucosa. Moreover, CaBP was detected mainly within the supranuclear region of the cytoplasm of absorptive cells and also at the level of their basal laminae. CaBP was not demonstrable either in the nuclei or associated with the brush border membrane of absorptive cells. Also, CaBP was neither detectable in goblet cells nor in sub-epithelial layers. When the specific anti-CaBP antiserum was replaced by nonimmune rabbit serum or when it was preabsorbed on a CaBP-Sepharose conjugate, no positive immunostaining was seen. Together with recent biochemical data our observations agree well with the view that CaBP may act as an intracellular "buffer" by protecting the cell against too high Ca2+ concentrations.

Polyclonal B cell activators (PBA) 1 are substances that directly activate B cells to clonal growth and antibody secretion by interacting with nonclonally distributed receptors on the surface of lymphocytes (1-5). The capability of B cells to respond to various PBA divides the B cell pool into different functional subsets that might or might not overlap with each other (6-9). Because polyclonal activation does not involve the variable region of immunoglobulin, the triggering is not immunologically specific, and, therefore, it has been proposed (6, 10) that the repertoire of antibody specificity is randomly distributed or even repeated among the "subsets" of B cell clones defined by reactivity to different mitogens. This proposal has been experimentally confirmed by observing increased antibody synthesis specific for conventional antigens or haptens induced by various PBA. These studies, however, did not take into account the extreme degeneracy of the immune system or, in other words, the great lack of precision in the fit betwen antibodies and antigens that can vary over a range of several orders of magnitude. Consequently, because of the extreme heterogeneity of the immune response, the question of whether different B cell subpopulations, as defined by mitogen reactivity, selectively express identical clonotypes has not been answered as yet. We decided to address ourselves to this question by comparing the expression of four idiotopes in spleen cells of BALB/c mice activated by two mitogens that have been described as acting on separate B cell subsets, i.e., lipopolysaccharide (LPS) and Nocardia delipidated cell mitogen (NDCM) (11).The 66, 137, and 395 idiotopes 2 are defined by BALB/c monoclonal antibodies against the monoclonal immunoglobulin (Ig) 174 to/~galactosidase produced by a BALB/c mouse. 3 None of these three determinants are normally expressed when BALB/c mice are immunized with flgalactosidase, and therefore they can be classified as nonrecurrent idiotopes. 3 Contrary to this, the M-460 idiotype (Id) specificity defined by the monoclonal anti-M460 antibody F6(51) is present on a portion of antitrinitrophenyl (TNP) antibodies produced by BALB/c mice after immunization with thymus-dependent or thymus-independent TNP antigens (12).We therefore determined the approximate frequencies of LPS-and NDCM-sensitive B lymphocytes secreting Ig molecules that bear the 66, 137,395, and M-460 idiotopes.

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