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.
A gene encoding the lambda 5 light chain constant region was isolated from a genomic library from the SPE mouse strain (C lambda 5S). SPE is an inbred wild mouse strain belonging to the Mus 3 or Mus spretus group that has been genetically isolated from Mus 1 (the group to which laboratory mice belong) for a period of 1‐3 million years. The sequence of the C lambda 5S gene shows strong homology to C lambda 5 of (C57BL/6J x DBA/2)F1 both in the coding region (98% identity) and in the 5′‐ and 3′‐flanking regions (98 and 95% identity, respectively). Sequence comparison of C lambda 5 genes with C lambda 1 of BALB/c shows only few substitutions in the C lambda 5 coding regions and suggests that the three genes have a common ancestor. These data indicate that the C lambda 5 gene has evolved under strong selective pressure and probably encodes a functional gene product. The conservation of the C lambda 5 gene in various Mus species was observed by high stringency Southern blot analyses using a C lambda 5S probe on DNA sample from members of four different groups of wild mice. All the laboratory and wild mouse strains tested, including those with amplified sets of C lambda 1 and C lambda 2 hybridizing sequences, showed only single C lambda 5 hybridizing fragments. Little variation in size of restriction fragments detected with the C lambda 5 probe was seen in the different Mus species suggesting a high degree of conservation.(ABSTRACT TRUNCATED AT 250 WORDS)
Recently we determined the absolute frequencies of lipopolysaccharide (LPS) and Nocardia-delipidated cell mitogen (NDCM) -sensitive B lymphocytes from BALB/c mice secreting immunoglobulin (Ig) molecules bearing any one of three different idiotopes originally found on a monoclonal anti-fl-galactosidase antibody (1). These three idiotopes, 66, 137 and 395, are defined by syngeneic monoclonal antibodies against the monoclonal Ig 174 produced by a BALB/c mouse (C. Le Guern, E. Barbier, and D. Juy. Idiotypic heterogeneity of monoclonal anti-fl-galactosidase antibodies. Manuscript in preparation). Extensive studies by conventional immunization clearly demonstrated that these three determinants are not normally expressed at detectable level when BALB/c mice are immnized with fl-galactosidase and, therefore, can be classified as nonrecurrent idiotopes (Le Guern et al., see above). Our results, however, indicate that these specificities are not only part of the idiotypic repertoire of LPS-and NDCM-sensitive BALB/c B cells, but that they can be induced to expression with a frequency similar to that of a recurrent idiotype, i.e., M-460 (1, 2). Because the frequency of a given specificity (either antibody or idiotypic specificity) determined by mitogenic stimulation does not require the presence of antigen, this analysis was not dependent on a particular protocol of immunization, but rather reflected the absolute frequencies of competent B cells in a steady state. Thus the discrepancy found between antigenic and polyclonal activation with regard to idiotope(s) expression may very well reflect independent expression of these V region markers and antigen-binding sites. The existence of defined idiotopes on immunoglobulins without known antigen specificity has been fully documented for some considerable time (3-6) but, up until now, it has been difficult to establish the possible existence of well-defined rules that govern the relationship between idiotopes and antigen-binding sites. Such studies have been hampered by the difficulty of selecting B cell clones or hybridomas that are positive or negative for any possible combination of a number of well-defined sets of V regions. Here, however, we were able to address this problem, because we knew the absolute frequencies of each of our three idiotopes and therefore could select and study individual clones of mitogenreactive B cells positive for any possible combination of these determinants and correlate them to anti-/~-galactosidase activity. The results presented here indicate
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