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 nude and 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.