FIG 4.

Loss of chitin in Pneumocystis cell wall. P. murina-infected lung tissue (A) and C. albicans-infected kidney tissue (positive control) (C) were stained with a recombinant chitin binding domain (green). Chitin staining is absent in P. murina (A) but readily detected in C. albicans (C). (B) Pneumocystis organisms are demonstrated by dual staining with anti-Msg (red), which labels both trophic forms and cysts, and dectin-Fc (green), which labels β-1,3-glucan in cysts. Original magnification, ×400.