CD4 and infection: When Tcra−/− mice were preinfected with CnH99 (100 yeasts, i.n.)and transferred CD4+ T cells (106 cells, i.v.)(C-IRIS condition, detailed in Fig. 1A), the respiratory rate and oxygen saturation levels were significantly reduced compared with control groups (naive Tcra−/−, Tcra−/− mice with CnH99 infection alone, and Tcra−/− mice with CD4+ T transfer alone) (Fig. 1B).