Contrasting effects of BCG on spleen and lymph node antibody responses in nude and normal mice

Subcutaneous footpad injection of BCG causes a marked augmentation of popliteal lymph node plaque forming cell (PFC) responses to DNP derivatized hemocyanin and to sheep red blood cells, both T dependent antigens, but not to DNP derivatized Ficoll, a T independent antigen. This augmentative effect occurs in normal thymus bearing heterozygous (nu/+) mice, but not in congenitally athymic nude mice (nu/nu). In contrast, intravenous injection of BCG causes a suppressed splenic PFC response to subsequently administered T dependent or T independent antigens in both nu/+ mice. BCG's augmenting effect on the lymph node appears to be mediated by a T helper cell. BCG's suppressive effect in the spleen is not attributable to T cells. The actual mechanism of the BCG mediated suppressive splenic effect remains incompletely defined at present.