Plaque-forming cells in rabbits immunized with BCG bacilli

Immunosuppressive activity of BCG: effects of adjuvant disease, lymphocyte subpopulations, and homing of thoracic duct cells in rats

Administration of BCG by various dosage schedules suppressed adjuvant disease in rats. BCG administration produced an initial increase, followed by a depression, of the phytohemagglutinin response of purified blood lymphocytes. An increase in absolute and relative numbers of bursa-equivalent (B)-cells followed BCG administration, concurrent with a decrease in the phytohemagglutinin responsiveness. With adjuvant alone, there was a diminution in phytohemagglutinin response and an increase in number of B-cells; the latter occurred immediately after adjuvant injection and also when the generalized disease appeared. When both BCG and adjvant were present, parallel increases of phytohemagglutinin responsiveness and B-cell numbers resulted. The pattern of tissue localization of radioactively labeled thoracic duct cells from normal or BCG-treated donors given to normal, BCG-treated, adjuvant-injected, and BCG-treated + adjuvant-injected syngeneic recipients indicated significantly greater homing to the thymus and decreased localization to the bone marrow when BCG had been given to either donors or recipients. When labeled thymus cells were used, only the decreased bone marrow localization was noted. These observations suggest that the suppressive effect of BCG may be mediated through modification of the lymphocyte recirculation pattern, possibly resulting from alterations in lymphocyte recognition sites.

Immune response to Mycobacterium leprae: plaque-forming cells in mice

Intravenous immunization with a cell extract of Mycobacterium leprae produced a primary immune response of considerable magnitude, followed by an equally large response after secondary stimulation, as measured by assay of plaque-forming cells (PFC). Infection with M. leprae or immunization with cell extract by the footpad route produced a lower level of response than that seen in the intravenous group. Identical patterns of response, although not of the same magnitude, were observed after both primary and secondary challenges in the two footpad groups, one infected with viable M. leprae and the other immunized with M. leprae cell extract. The secondary response after a booster dose to all these groups appeared to be an enhanced immunoglobulin M response. Control studies confirmed that the immune response was a direct result of the host-parasite interaction and that the PFC observed resulted from stimulation of antibody-forming cells by antigens of M. leprae. The similarity in time of appearance of peak PFC levels in the two footpad groups may be attributed to the live challenge passing through a latent phase. Alternatively, the challenge is known to contain a large proportion on nonviable cells, and it may also contain soluble M. leprae antigens. Studies of the cross-reactivity of the antigens have extended previous observations on antigens shared between M. leprae and other mycobacterial species. Use of the two antigen-containing fractions of the M. leprae cell extract has suggested that one of the fractions contains some shared antigens, whereas the other has an antigen specific to M. leprae.