Antigen binding and idiotype analysis of antibodies obtained after electroporation of heavy and light chain genes encoding phosphocholine-specific antibodies: a model for T15-idiotype dominance.

Abstract

SununaryAntibodies bearing the T15 idiotype dominate the murine primary immune response to phosphocholine (PC). Analysis of antigen binding of antibodies derived from VI:DFL16.1:J.1 (V.1) germline and N region-derived variant heavy (H) chains and g22, K24, and K8 light (L) chains demonstrates that the T15H:K22L (T15) antibody binds PC at least 20-40 times better than other antibodies derived from alternate germline forms of the V.1 H chain and g22, K24, or K8 L chains. To achieve af~nities in the same range as the T15 antibody, K24 and Ic8 L chain-containing antibodies must have H chains derived from variant N region or somatically mutated V.1 genes. Single amino acid differences at the VD junction of the various germline and N region variant V.1 H chains dictate the L chain that can associate with the H chain to produce a PC-specific antibody. Several H:L combinations give rise to T15 or M167 idiotypepositive antibodies that lack specificity for PC, and single amino acid substitutions or insertions at the V.I:D junction result in the loss of T15 or M167 idiotopes. Based on these observations, our data support a molecular model involving both preferential gene rearrangement and antigendriven B cell selection to explain T15 idiotype dominance in the immune response to PC. In the absence of N region diversification, large numbers of neonatal B cells bearing the T15H:K22L surface immunoglobulin M (slgM) receptors would be selected and expanded by autologous or environmental PC antigen into the long-lived peripheral B cell pool.T he primary antibody response to PC in normal inbred mice is dominated by antibodies expressing H and L chain products of the V.1 and V~22 germline genes (1, 2). These antibodies are identical to the antibody produced by the T15 plasmacytoma (3). The T15 clone of B cells is present in the mouse spleen at a higher frequency than any other individual clone of B cells and comprises >75% of all phosphocholine (PC)l-specific B cells in normal mice (4). The reasons for T15-Id dominance of the anti-PC immune response are not fully understood; however, idiotype network selection, binding-site affinity, and preferential V gene expression have I Abbreviation used in this paper: PC, phosphocholine. all been suggested. A. J. Feeney (5) has recently shown that over 50% of the V1:DFL16.1junctions produced in neonatal pre-B cells have prototypic T15 V-D junctional sequences, and has hypothesized that this preferential recombination of these germline genes would account for the dominance of T15 clones in the anti-PC repertoire. If the prototypic T15H chain is preferentially produced and this H chain can only form a PC-specific antibody with a K22 L chain, the subsequent receptor-driven selection and amplification of this clone into a long-lived B cell pool could account for T15-Id dominance. This hypothesis is supported by our recent observation (6, 7) that PC-specific B cells in M167 H chain transgenic mice are selected and amplified by a receptor-mediated, antigen-driven process after they emerge from ...

Repertoire Shift in the Humoral Response to Phosphocholine-Keyhole Limpet Hemocyanin: VH Somatic Mutation in Germinal Center B Cells Impairs T15 Ig Function

“…Both rearranged V H 1-DFL16.1-JH1 genes as well as rearranged V 22-J 5 genes were readily amplified from microdissected single germinal centers before the repertoire shift in serum Ab. Although we have not formally demonstrated the presence of T15 V H and V L genes within a single cell, the V 22-J 5 L chains form functional PC binding sites only when paired with the T15 H chain (41). Taken together, the amplification of canonical T15 H and L rearrangements within cells of the same germinal centers supports our immunohistochemical identification of T15 Id ϩ cells.…”

Microbial Modulation of Host Immunity with the Small Molecule Phosphorylcholine

“…B1 antibodies are part of the repertoire of IgM synthesized prior to microbial exposure and have lower affinity than antibodies induced following infection (96). The major idiotype of anti-ChoP antibodies is T15, originally identified in mice (97,98). While ChoP modification of host molecules, including the major cell membrane lipid phosphatidylcholine, is very common, it has been shown that T15 antibodies do not recognize the ChoP epitope in intact human membrane lipids (99,100).…”

Highly reduced protection againstStreptococcus pneumoniaeafter deletion of a single heavy chain gene in mouse

“…Each V1 variant expresses a different V:D junction and pairs with a different light (L) chain to form a PC-binding Ab. The germ line T15 V1 H chain (95H-Asp) associates with 22 L chain, the M603 variant (95H-Asn) associates with 8 L chain, the M167͞ M511 variants (96H-Ala) associate with the 24 L chain, and the D16 variant (95H-Gly) associates with the 1c L chain (13,14). These V H 1-id ϩ Abs, with the exception of the D16-like variants, are generally highly protective against SPn in passive transfer assays (6,12).…”