Genetic selection for antibody responsiveness in mice: further evidence for inverse modification of macrophage catabolic activity without alteration of the expression of T-cell-mediated immunity.

Five selective breedings have been performed for the character "antibody production" in mice. Two of them, Selection I and Selection II, carried out for maximal (H) and minimal (L) antibody response to heterologous erythrocytes, gave similar results concerning the genetic parameters and the extent of modification of antibody response to unrelated antigens (non-specific effect of the selection). Macrophage characteristics and the expression of T-mediated immunity were investigated in H and L mice of Selection II and compared with results already obtained in Selection I. The phagocytic activity of macrophages was similar in the two lines, whereas an important interline difference was observed concerning the persistence of the immunogen, which was much shorter in L than in H mice. The more rapid antigen catabolism in L mice explains why the threshold immunogenic dose was higher in these mice and why the antibody response was much more improved in L than in H mice by repeated antigen administration. Results on skin allograft rejection, delayed-type hypersensitivity and responsiveness to T mitogen demonstrated that H and L mice have a similar ability to mount T-mediated immunity reactions. Two findings obtained in Selection I were therefore confirmed: 1) macrophage catabolic activity is modified by selection in the opposite direction of antibody production: low antibody responsiveness is associated with high macrophage activity and vice-versa; 2) and the expression of cell-mediated immunity and of the humoral immune response are at least partially under independent genetic regulation.