Specificity of H‐2‐linked Ir gene control in mice: recognition of defined sequence analogs of (T, G)‐A–L

Abstract

In order to study the specificity of H‐linked Ir gene control in more detail the polypeptide poly(LTyr, LGlu>poly(DLAla)–poly(LLys) ((T, G)‐A‐L) was modified by replacing the (T, G) copolymers by various defined tyrosine‐containing oligopeptides. It was found that the antibody response to all of the analogs of (T, G)‐A–L tested was influenced to some extent by H‐2‐linked Ir gene(s), the response pattern being concordant with that of (T, G)‐A–L. Some of the antigens carrying structurally and serologically distinct oligopeptides were as efficient with respect to high/low responder discrimination as (T, G)‐A–L, others including the core polypeptide A‐L itself were weakly immunogenic and gave only a small high/low responder split. Certain experimental data indicate that in addition to the tyrosine peptides the poly‐DL‐alanine side chains may play an important role for the recognition of these polypeptides. The possibility that the common response pattern could be due to an Ir gene specific mainly for the DL‐alanine peptides is discussed. Specificity of genetic control would then be relatively independent of the serological specificity of the tyrosine peptides. On the other hand, recognition of the analogs and of (T, G)‐A–L could be controlled by separate but closely linked Ir genes specific for each of the terminal peptide determinants which probably include the adjacent alanine residues. Genetic factors outside the H‐2 complex have in addition to the H‐linked Ir genes been found to exert a strong influence on the antibody response to some of the analogs of (T, G)‐A–L.

Specificity of H‐2‐linked Ir gene control in mice: Recognition of the core structure A–L in defined sequence analogues of (T,G)‐A–L

“…For instance, one possibility to explain the common pattern of Ir gene control would be that these antigens, which all contain tyrosine residues, might not be distinguished immunologically at the Ievel of helper T cells. On the other hand, some indications have been obtained previously [17] that the common core structure A--L plays an important role for the genetic control mechanism. If confirmed, this would favor a function of Ir genes on a level which is different from that of the antigen receptor.…”

“…It has been reported previously [16] that several synthetic polypeptides, structurally related to (T,G)-A--L but differing from each other, showed a similar high-low responder split in H-2b and H-2k mice as (T,G)-A--L; and, in several cases, the respective Ir genes could also be localized in the I-A subregion [17]. These antigens are used here as tools to study the Ir gene function by analyzing their specific reactions on the B and T cell level and by comparing them with data on the specificity of Ir gene control.…”

“…The branched polypeptide S--L was prepared from a backbone of poly-L-lysine (average degree of polymerization n = 80) in the same way as described for A--L [17], except that the N-carboxy anhydride of sarcosine (N-methylglycine) was used instead of DL-alanine. Hexatyrosine peptides (T6) were then attached to about 35% of the polysarcosine side chains.…”

“…The average molecular weight of this polymer was 50000. Peptide side chains were attached by methods analogous to those used for the A--L series of antigens [17]. In T2G2--PVA, an average of 15 T2G2 peptides were bound per molecule of PVA.…”

“…For technical reasons, different immunization procedures were used for the various assays. For assaying antibody responses in different mouse strains, mice received 10 pg of the polypeptide in complete Freund's adjuvant (CFA), 10 pg of antigen in 0.15 M NaCl on day 21, and were bled on day 31 as described previously [17]. For inhibition tests, large amounts of antibodies were needed from individual mice.…”