Affinity and avidity of antibodies to the random polymer (T,G)-A-L and a related ordered synthetic polypeptide

Abstract

The affinity values of antibodies to the random synthetic antigen poly-(Tyr,Glu)-poly(dl Ala)-poly(Lys) [known as (T,G)-A-L] and to the ordered (Tyr-Tyr-Glu-Glu)-poly(dlAla)-poly(Lys) [known as (T-T-G-G)-A-L] were measured. Determinations of the association constants were performed by antigen binding capacity assay, ABC, using the whole antigen, and by equilibrium dialysis, using a radioactive conjugate of the ordered peptide T-T-G-G which was found to represent the major determinant of the random (T,G)-A-L. The affinity values of antibodies elicited by high responder mice to (T,G)-A-L and to (T-T-G-G)-A-L were found to be similar. However, a difference of two orders of magnitude was found between the values obtained by the two methods. This difference is partially explained by probability analysis.

Upon immunizing low responder (H-2^k) mice with complexes of the antigens with methylated bovine serum albumin (MBSA), an increase in their antibody response was observed. The affinity values of these antibodies were found to be similar to those of high responder antibodies after immunization with either the antigens complexed to MBSA or with the antigens alone. On the basis of these data we conclude that low responder (H-2^k) B cells have the potential to produce antibodies of the same specificity and quality as the high responders to the random (T,G)-A-L and to the ordered (T-T-G-G)-A-L, and that the genetic defect in these mice should be located at the level of the B-cell acceptor for the T-cell signal.