FIGURE 1.

Rac is involved in NK anti-cry1ptococcal killing. A, YT cells were stimulated with Cryptococcus, and levels of Rac-GTP were measured by immunoblotting. B, densitometry of normalized Rac-GTP/total Rac of the mean of three experiments. C, YT cells were preincubated with U73122 or DMSO control and co-cultured with Cryptococcus overnight. The data are representative of three experiments. D, PBMC were labeled with carboxyfluorescein succinimidyl ester and stimulated with phytohemeagglutinin for 5 days in the presence of DMSO or U73122. A reduction in fluorescence intensity indicates proliferation. The data are representative of three experiments using PBMC from three donors. E, YT cells were preincubated with EHT 1864 or Rac inhibitor II and stimulated with C. neoformans. The levels of Rac-GTP were determined. The data are representative of two experiments. F and G, YT cells were co-incubated with Cryptococcus overnight in the presence or absence of EHT 1864 (F) or Rac (G) inhibitor II. F and G are representative of three and two independent experiments, respectively. H, primary NK cells were co-cultured with Cryptococcus in the presence of EHT 1864 or H₂O control. I, levels of Rac1 in transfected YT cells were analyzed by immunoblotting. J, YT cells were transfected with nontargeting siRNA or two different sequences of Rac1 specific siRNA. Transfected cells were used in a killing assay with C. neoformans. The data were representative of three experiments. The data were all analyzed using one-way analysis of variance with Bonferroni correction. Cryptococcus strain B3501 was used in all experiments. *, p < 0.05; **, p < 0.01; ***, p < 0.001. Error bars represent S.E. C+YT, YT co-cultured with Cryptococcus; CA, Cryptococcus alone; YT, unstimulated YT cells.