However, the role of CD4+ T cells in non-HIV-PCP patients is not as prominent, and they are mainly valuable for identifying specific individuals at particularly high clinical risk of PCP, such as recipients of allogeneic hematopoietic stem cell (Castagnola et al., 1995), patients with solid malignancies undergoing chemotherapy (Sepkowitz et al., 1992), organ transplantation patients, and individuals with hematological malignancies (Mansharamani et al., 2000a). This evidence concerns the gene CD4 and pneumocystosis.