A. Cell proliferation following immunization with crude Pneumocystis antigens. Splenocytes from animals that were immunized four to five times with crude antigens were cultured in triplicate with recombinant P. murina Msg proteins (n = 5 except n = 3 for MSG119Am), crude Pneumocystis antigens (n = 5), and purified native Msg (n = 2). Non-immune animals or animals immunized with normal lung antigen were used as controls and splenocytes were cultured with the same antigens (n = 4 for all except n = 3 for MSG119Am and n = 1 for purified native Msg). Bars represent the stimulation index (SI) as compared to appropriate vector without Msg for recombinant antigens, normal lung antigens for crude Pneumocystis antigens and no antigen for native Msg. B. Antibody reactivity to each of the antigens measured by ELISA. Serum samples were run in duplicate for each antigen. Each bar in B represents the mean optical density for each antigen in Pneumocystis antigen immunized or control immunized animals (the same number of animals were used as for A). Unpaired t tests were used to compare the results for immunized animals to control (normal lung immunized) animals. Statistical significance is indicated by the following symbols: *, p ≤ 0.05; ‡, p ≤ 0.01; †, p ≤ 0.001. For native Msg statistical significance was not calculated due to the small number of animals.