FIG. 1.

Control of in vitro C. neoformans infection by PBMC prestimulated with heat-killed C. neoformans. PBMC (10⁶) were cultured with and without heat-killed organisms (2 × 10⁵), either B3501 (encapsulated) (A) or the CAP67 mutant (acapsular) (B), for 12 days before live organisms of the same strain (1 × 10³ to 2 × 10³) were added in fresh medium with 10% PHS. The course of infection was followed by CFU counts, expressed as the percentage of cryptococcal growth in relation to the inoculum of live organisms. Data are means + SE from 10 independent experiments with different donors for B3501 and 6 independent experiments with different donors for the CAP67 mutant. Growth of encapsulated (at 6 days postinfection) (A) and acapsular (at 10 days postinfection) (B) C. neoformans was significantly reduced in the presence of stimulated compared with unstimulated PBMC (P = 0.001 and P = 0.03, respectively). (C and D) Corresponding CFU data for B3501 (C) and the CAP67 mutant (D). The mean inocula of live organisms were 1,490 and 1,270, respectively.