A predominant idiotype independent of specificity, or Ig and H-2 allotypes, is found in the primary but not the secondary murine antibody response to lysozyme

Transient dominance of the early primary immune response by a highly conserved B-cell clone that is distinguished by its lack of memory, high threshold of activation, and a high affinity

We establish here that the very early primary response to the hapten phthalate (Xmp) is distinguished by a restricted heterogeneity with over 80% of the anti-Xmp antibodies expressing a single well-defined cross-reactive idiotype (CRIXmp-1) associated with a previously described highly conserved clonotype that is expressed by most inbred strains of mice and many outbred mouse populations as well. The characteristic early dominance of this one clonotype in the primary response is transient. While the CRIXmp-1 clonotype is present later in the primary and throughout the secondary response, it represents only a very small proportion of the total anti-Xmp antibody population at these times. The early dominance of the single clonotype is rapidly replaced by a heterogeneous population of antibodies. Differential activation thresholds for the primary response clonotype (CRIXmp-1) and secondary response clonotypes, and the failure of the dominant primary response clonotype to expand in the secondary response (i.e., absence of memory) suggest the presence of two distinct B-cell lineages.

Use of substituted and tandem-repeated peptides to probe the relevance of the highly conserved RGD tripeptide in the immune response against foot-and-mouth disease virus

Antigenic site A of foot-and-mouth disease virus (FMDV) is an exposed, mobile loop which includes a central, highly conserved Arg-Gly-Asp tripeptide (RGD, VP1 residues 141-143 in serotype C) thought to be part of the cell attachment site. We have analyzed the contribution of RGD to the interaction of site A with antibodies by incorporating selected amino acid replacements at RGD into synthetic peptides representing site A, and analyzing the reactivity of substituted peptides with site A-specific monoclonal antibodies (MAbs). Replacement of Arg-141, Gly-142 or Asp-143 by alanine resulted in the loss of one, three and five epitopes, respectively, out of seven epitopes probed. Other replacements resulted in the loss of even larger numbers of epitopes, suggesting that the amino acids of the RGD region are either directly involved in interaction with antibodies or that they exert an important influence on the interaction of surrounding residues with antibodies. Thus, we explored the ability of tandem repeats of the RGDL sequence (corresponding to FMDV C-S8c1) to evoke neutralizing antibodies in rabbits and guinea pigs. Neutralizing activity was generally low but with a broad specificity for different FMDV serotypes and variants. Significant decreases in neutralizing titers were observed with boosting, suggesting a possible suppression of those anti-peptide antibodies which may also be directed to cellular RGD sequences. The results point to an involvement of RGD in the antigenic structure of site A, and open the possibility that broadly neutralizing antibodies might be induced by tandem repeats of the critical, conserved domain.

A B cell population that dominates the primary response to influenza virus hemagglutinin does not participate in the memory response

The early primary B cell response of BALB/c mice to the influenza virus A/PR/8/34 (PR8) hemagglutinin (HA) is dominated by B cells that utilize a single V kappa gene in association with one of two closely related VH genes. We have used an anti-idiotypic reagent that recognizes a light chain-associated idiotope (23-1 Id) on these antibodies to follow their presence during the anti-HA response. Quantitation of 23-1Id+ antibodies at different time points during the anti-HA response indicates that the 23-1Id+ B cell response peaks early after primary immunization and is not re-induced by secondary challenge. Furthermore, 23-1Id+ titers in serum decay rapidly between the first and second week after immunization, and the HA-specific 23-1Id+ precursor B cell population does not significantly expand in the months following immunization. These results indicate that despite their predominance during the primary response, 23-Id+ B cells abruptly disappear from the response and do not mature into memory B cells.

Evidence for idiotypic sharing between conventional and naturally activated B cells

In the primary immune response to hen egg-white lysozyme (HEL), approximately 50% of the primary anti-HEL antibody-forming cells (AFC) express IdXE, an idiotype absent from the secondary response. Spontaneous IgM enzyme-linked immunosorbent assay (ELISA)-AFC in spleen cells from naive A/J mice were analyzed for the occurrence of IdXE by use of two affinity-purified rabbit antisera, R213 and R8, each raised against a different primary IdXE+, anti-HEL mAb. Two ELISA-AFC assay methods were used: direct coating of immunoplates with R213 or development of IgM-producing ELISA-AFC with biotinylated R8. From ages 7 days until 6 months, 10-20% of spontaneous IgM AFC were found to be IdXE+. IdXE+ anti-HEL IgG1 monoclonal antibodies, 2F4 or 3C11 (100 micrograms/ml), completely inhibited binding of biotinylated R8 (0.5 micrograms/ml) to spontaneous IgM-AFC while IdXE-, anti-HEL IgG1, 5E11 and 2C7, showed no significant inhibition. Greater than 90% of IdXE+ spontaneous IgM-AFC were not HEL specific. We conclude that a dominant set of idiotopes found in a conventional antigen-driven immune response can also play a major role in the spontaneously activated B cell repertoire. Our data argue against a bifurcation of the immune system into a compartment of idiotypic network-related cells and an independent set of non-network cells subject to antigenic stimulation.

Inhibition of offspring response to HEL-CFA by administration of anti-HEL MAB to the mother is not related to the predominant idiotype, IdXE, or specificity of the MAB

In the neonatal suckling mouse, the antibody response to HEL-CFA can be inhibited by administration of certain anti-HEL monoclonal antibodies to the mother. The murine primary response to hen egg-white lysozyme (HEL), which can be elicited in A/J mice as early as 7 days of age, is characterized by a predominant specificity that includes the 3 N-terminal amino acids of HEL (TIP-dependence) and by a predominant idiotype, IdXE. A panel of murine IgG1 anti-HEL mAbs was administered to the suckling offspring via the mother. These mAbs were not equivalent in their effects on the offspring. Only two of six IgG1 mAbs, 2F4/2E5 (IdXE-positive, TIP-dependent) and 2D1 (IdXE-negative, TIP-independent), consistently induced suppression of the response of A/J offspring when immunized at 16-20 days of age with HEL-CFA. Suppression averaged 71% for 2F4/2E5 and 74% for 2D1 and was always statistically significant (P less than .05) when 275 micrograms mAb was administered IP to the mother within 24 hr postpartum. Since 2D1 is IdXE-negative and TIP-independent, neither of these properties appears to be crucial for suppression. Differences in transfer of the mAbs from the mother to the offspring or differences in catabolism of the mAbs in the offspring were not detected. When various characteristics of the mAbs such as affinity, idiotypy, and fine specificity were considered, there was no single factor which determined suppression. One of the two mAbs that suppressed the offspring response, 2D1, is idiotypically highly connected in the anti-HEL mAb panel. This observation suggests that idiotypic interactions in the developing neonatal repertoire with subsequent perturbation of T and B cell repertoire development may be an area for future investigation.