Suppressive activity of splenic macrophages induced by transparent and opaque colonial variants of Mycobacterium avium complex against lymphoproliferative response.

Splenic macrophages (M phi s) induced by the two colonial variants of Mycobacterium avium complex, SmT variant (smooth, transparent, flat) and SmD variant (smooth, opaque, domeshaped), were studied for their suppressive activity against mitogenic response of splenic T cells to concanavalin A (ConA). The SmT variant is much more virulent than the SmD variant and causes more severe infection in host mice. Moreover, suppressed state of ConA mitogenic response of host spleen cells persisted much longer in SmT-infected mice than in SmD-infected ones. However, the suppressive activity of SmT-induced M phi s, induced around 2 weeks after infection, against lymphoproliferative response was significantly weaker than SmD-induced M phi s. In contrast, the former M phi s showed somewhat higher active oxygen-producing ability than the latter, as based on the chemiluminescence. These findings indicate that the immunosuppressive M phi s transiently induced in the early phase of M. intracellulare infection hardly affect the host resistance to the organisms and, thus, play relatively minor role in the progression of the infection.