Fig. 4.

Yeast cells are ingested more efficiently than hyphal cells by J774 macrophages. Competition assays were performed with various combinations of S. cerevisiae, C. glabrata, and C. albicans yeast or hyphal cells (preincubated for 20 min with 20% serum at 37°C to induce hyphae). Equal numbers of yeast cells expressing yEmRFP or yEGFP were mixed together and added to J774 macrophages at an MOI of 5. After 40 min, CW was added and red or green cells were scored as being in or out of macrophages. (A) Graphic representation of quantitative competition assays between nontagged C. albicans yeast cells (strain SKY51) and those expressing yEGFP (strain SKY43) that were mixed with RFP-expressing C. albicans yeast cells (strain SKY38), with S. cerevisiae yeast cells (strain SEY6210 plus pADH-yEGFP), or with C. albicans hyphal cells (strain SKY38). Sc, Ca, and Cg, S. cerevisiae, C. albicans, and C. glabrata, respectively. The percent internalization ratio was calculated by scoring yeast cells as red or green and as CW positive (outside) or CW negative (inside), as described in Materials and Methods. Representative single-focal-plane images of these assays are shown in panel B, with arrows highlighting single macrophages that have taken up both red and green yeast cells at various ratios.