A common idiotype in IgE and its relation to recognition of the grass pollen allergen Phl p 2.

The variable regions of allergen-specific IgE, the isotype mediating allergic responses, are poorly defined to date. In this study we define the character of human antibody binding sites recognizing Phl p 2, a major allergen from timothy grass pollen. Independently raised specificities developed by phage display technology tended to have common sequence motifs (idiotypes), such as IGHV4-31 germline gene origin and heavy chain complementarity-determining region (CDR) 3 length and sequence. They also combined with highly related light chain sequences. Such heavy chain variable domain-encoding transcripts have also been found in the IgE-encoding transcriptome of yet other grass pollen allergic subjects. Altogether these data argue that a common idiotype is used to establish specific antibodies with a potential to mediate allergic responses to Phl p 2. Such a restriction may contribute to the limited molecular diversity observed in some IgE populations.

Properties of murine antibodies from different V region families specific for bromelain-treated mouse erythrocytes.

We have analyzed the combining site diversity of murine antibodies reactive with bromelain-treated mouse RBC (BrMRBC) in B10.A mice. Although several VH and V kappa genes are used to generate antibodies of this specificity, two combinations account for more than 80% of the repertoire from the spleen: VH11/V kappa 9 and VH12/V kappa 4. Antibodies representing these two predominant groups were found to correspond to two previously reported distinct cross-reactive Id families accounting for most of the anti-BrMRBC reactivity in several strains of mice. mAb of the VH11/V kappa 9 type bound the haptens trimethyl-ammonium and phosphorylcholine much more avidly (approximately 1000 fold) than did the VH12/V kappa 4 type antibodies. Both of these haptens represent constituents of phosphatidylcholine, which BrMRBC-specific antibodies are reported to bind. Despite this differential reactivity, members of both the VH11/V kappa 9 and VH12/V kappa 4 antibody groups lysed BrMRBC with similar efficiencies. These data suggest that the two major classes of BrMRBC-specific antibodies have at least partially different specificities and imply that the events that lead to their high frequencies in the CD5+ repertoire may result from different selective forces.

H-2 control of expression of an idiotype shared by normal B cells and a B-cell lymphoma.

The spleens of normal B10.H-2aH-4bp/Wts (2a4b) mice contain cells which, in response to mitogen stimulation, secrete hemolytic antibody specific for a determinant present on both sheep and bromelain-treated mouse erythrocytes. These cells were found to be Ly-1 positive. Approximately 50% of these cells bear surface immunoglobulin (sIg) with the same idiotype as the sIg of a 2a4b-derived B-cell lymphoma, CH12. Backcross analysis revealed H-2 control of the frequency of the idiotype-positive B cell. The regulatory gene did not correlate with the Igh-1 allotype, and analysis of 22 inbred mouse strains mapped the gene to the I-E subregion. Surprisingly, only strains homozygous for Ek alpha expressed the idiotype, and expression was a recessive trait. Possible mechanisms for this control of idiotype expression and its relation to lymphomagenesis are discussed.

The asymmetry in idiotype-isotype expression in the response to phosphocholine is due to divergence in the expressed repertoires of Lyb-5+ and Lyb-5- B cells.

The X-linked CBA/N immune defect was used to investigate the roles of Lyb-5- and Lyb-5+ B cells in the memory response to PC-KLH (phosphocholine-conjugated keyhole limpet hemocyanin). (CBA/N X BALB/c)F1 (CB) male mice express the xid mutation and thereby lack the Lyb-5+ B cell subset, whereas their female littermates are normal and express both Lyb-5+ and Lyb-5- B cells. After priming with PC-conjugated hemocyanin (PC-Hy) in complete Freund's adjuvant, female B cells produce three phenotypic sets of PC-KLH-specific antibody. The first set (group I) is dominated by T15+, IgM, IgA, and IgG3, PC-specific antibodies. The second subset (group II) is specific for phenylphosphocholine (PPC), and is dominated by T15-, IgG1, and IgG2 antibodies. The third set (group III) recognizes an epitope(s) composed of both the PPC hapten and carrier determinants. PC-Hy-primed B cells from immune defective CB male mice produce the same number of IgG1 and IgG2 plaque-forming cells (PFC) as do PC-Hy-primed normal female cells, and these PFC are also predominantly T15- and PPC specific (group II). In addition, a significant amount of group III IgG1 and IgG2 antibody is observed in the immune defective male response. In contrast to female B cells, immune defective male B cells produce a low IgM, IgA, and IgG3 memory response that is not composed of PC-specific (group I) antibodies; in fact, most of these antibodies arise from group III precursors and are not inhibited by either PC or PPC. PC-specific antibodies usually represent less than 25% of the anti-PC-KLH response in immune defective mice; however, these PC-specific antibodies are predominantly T15-. These data suggest that the Lyb-5-B cells in both normal and immune defective mice produce the T15-, IgG1, and IgG2 antibodies that dominate the secondary immune response to PC-KLH, and that the Lyb-5+ B cells produce the T15+, IgM, IgA, and IgG3 portion of the secondary response in normal mice. This hypothesis was confirmed by priming normal mice with the R36a strain of Streptococcus pneumoniae or with PC-Hy in saline. These forms of PC-antigen prime only the Lyb-5+ B cell subset. The adoptive transfer of these two B cell sources results in an anti-PC-KLH response that is T15 dominant and totally PC inhibitable.(ABSTRACT TRUNCATED AT 400 WORDS)