Antibody response elicited by T-dependent and T-independent antigens in gene targeted kappa-deficient mice

Animal models substantially contribute to the understanding of the pathogenesis of various human diseases, including those associated with genetic defects. Our study investigated the characteristics of antibody responses elicited by T-dependent and T-independent antigens in mice rendered kappa-deficient by targeted deletion of the J kappa C kappa gene segments. It is known that in normal murine species the kappa repertoire dominates the antibody repertoire (kappa/lambda ratio = 95:5). Our results indicate that the kappa gene deletion causes the alternative usage of lambda 1 (93%) and lambda 2 (7%) light chains, confirming previous studies demonstrating that in kappa-deficient mice all B cells express Ig lambda receptors. The anti-trinitrophenylbenzene (TNP) response in K-/- mice was compensated for by lambda 1 and lambda 2 bearing Igs. However, isoelectric focusing analysis of anti-TNP antibodies showed a considerably more restricted pattern of lambda anti-TNP antibodies in K-/- as compared with kappa antibodies in normal mice. No major differences were observed in the affinity for the hapten of kappa or lambda 1 or lambda 2 mAbs obtained from 129/Sv and K-/- mice. Furthermore, lambda 1 and lambda 2 chains can reconstitute the expression of an idiotype (460Id) borne on kappa anti-TNP antibodies. The 460Id was detected both in polyclonal and monoclonal anti-TNP antibodies obtained from K-/- mice. Our results clearly showed that the kappa anti-TNP repertoire is compensated by the lambda repertoire even though the latter is clonally restricted in K-/- mice.