Genetic control of T helper cell function in the clawed toad Xenopus laevis

The genetic control of the collaboration between Xenopus T and B cells has been analyzed in vivo using cells from five strains of major histocompatibility complex-defined Xenopus. When carrier (fowl gamma-globulin)-primed T cells and hapten (dinitrophenylated keyhole limpet hemocyanin)-primed B cells differed by minor histocompatibility antigens or by only one haplotype of the major histocompatibility complex, the collaboration was efficient in the sense that large numbers of plaques, low-molecular weight antibodies and high-affinity IgM antibodies could be recorded in the cultures challenged with dinitrophenylated fowl gamma-globulin. However, when T and B cells differed at both alleles of the major histocompatibility complex, lower numbers of plaques were obtained, no low-molecular weight anti-hapten antibodies could be detected, and the IgM antibodies that were sometimes synthesized were of low affinity. This suggests that the major histocompatibility complex, or a gene linked with it, affects the collaboration between Xenopus T and B cells in a way perhaps similar to that described in mammals.