FIG. 5.

Treatment with non-heat-inactivated human serum or anticapsular MAb augments lymphocyte proliferation in response to CPS-coated acapsular C. neoformans 67. PBMC (□) were stimulated with untreated C. neoformans (■) or C. neoformans that had been preincubated with 10 μg of purified CPS per ml (). CPS-treated organisms were incubated in human serum (HS) (A) or with 10 μg of MAb to polysaccharide per ml (B) (▥). In panel A the percentage of cells that had taken up CPS-treated C. neoformans increased from 8% of cells without serum to 29% of cells with serum opsonization. In panel B the percentage of cells that had taken up CPS-treated C. neoformans increased from 10% of cells in the absence of antibody to 45% of cells in the presence of antibody. ∗, P < 0.05 compared to PBMC plus C. neoformans. †, P < 0.05 compared to PBMC plus CPS-treated C. neoformans. The experiment was repeated three times with similar results.