Co-selection of the rare T cell receptor-γ B haplotype in mouse lines selected for low responsiveness to red blood cell antigens

Tcell receptor (TcR)-γ haplotype was investigated in seven pairs of murine Biozzi lines selected for low and high antibody (Ab) response to different antigens (Ag). High-responder lines (H) express γA or γC haplotypes irrespective of the selecting Ag. In contrast, the γB haplotype, which is rare in laboratory mouse strains, is found in all Iow-responder lines (L) to sheep erythrocyte Ag (SE). However, the TcR-γB locus might only have a low penetrance in the control of the SE response. Moreover, investigations using LIVA mice, which were selected for low SE response from homozygous γA founder parents, indicate that the γB haplotype is neither necessary nor sufficient to achieve a low-responder phenotype. The γB haplotype might, thus, be co-selected to confer to L mice an improved resistance to bacterial infections mediated by γδ5 T cells compensating the profound and nonspecific immune perturbation associated with the low Ab response.