Pneumocystis carinii pneumonia (PCP) is a life-threatening opportunistic lung infection caused by the human-specific opportunistic fungus Pneumocystis carinii (Sokulska et al., 2015), commonly seen in immunocompromised individuals with a combination of human immunodeficiency virus (HIV) infection (CD4+ cell count <200 cells/mm3), tumors, organ transplants, autoimmune diseases and other causes (Yale and Limper, 1996; Thomas and Limper, 2004). The gene discussed is CD4; the disease is pneumocystosis.