PROLIFERATIVE AND CYTOKINE RESPONSES TO A MAJOR SURFACE GLYCOPROTEIN OF PNEUMOCYSTIS-CARINII

Naturally derived T-cell responses by rats to a 120-kDa major surface glycoprotein (MSG) of rat-derived Pneumocystis carinii were analyzed i n vitro. Specific cytokines elicited by the T-cell response to the MSG were also identified. MSG was purified from rat-derived P. carinii by three different techniques: lectin affinity chromatography, sodium do decyl sulfate-polyacrylamide gel electrophoresis followed by electroel ution, and size-exclusion high-performance liquid chromatography. The cell-mediated immunity of spleen cells isolated from Lewis rats with a nd without natural exposure to P. carinii to the purified MSG was stud ied. Exposure to P. carinii was monitored by the presence or absence o f serum antibodies to P. carinii antigens by Western blotting (immunob lotting). A T-cell proliferative response to the MSG was identified on ly with spleen cells isolated from rats exposed to P. carinii and peak ed at 4 days. Flow cytometric analysis revealed that the percentage of CD4 cells was significantly increased during the proliferative respon se to MSG. MSG also elicited secretion of tumor necrosis factor alpha, interleukin-1, and interleukin-2, with peak activity of these cytokin es occurring after 12, 24, and 48 h, respectively, of culture. These f indings suggest that MSG is important in host T-cell recognition of an d immune response to P. carinii by recruitment of inflammatory cells a nd cytokine production.