Variation in immunogenicity of mycobacteria: role of antigen-presenting cells.

The antigen-presenting efficiency of peritoneal cells and irradiated spleen cells was compared using Mycobacterium tuberculosis- and M. vaccae-primed T cells and corresponding sonicates as antigens in an in vitro lymphocyte transformation test. The presentation efficiency of irradiated spleen cells was reasonably good for both antigens. However, with peritoneal cells as the antigen-presenting cells, the proliferative response against only M. tuberculosis sonicate was good. Proliferation of M. vaccae-primed T cells was very poor when the antigen was presented by peritoneal cells. Poly I:poly C treatment of mice prior to harvesting the peritoneal cells resulted in distinct improvement in their efficiency to present M. vaccae sonicate; maximal proliferative response was obtained with peritoneal cells from mice receiving two and three doses of poly I:poly C 24 hr apart. Even paraformaldehyde-fixed peritoneal cells from poly I:poly C-treated mice gave an efficient M. vaccae-specific stimulation to primed T cells. Based on these data, it was concluded that failure of mice to respond to M. vaccae by intraperitoneal immunization is the result of the poor efficiency of presentation of M. vaccae antigen.