(A) Antitumour mechanisms of PCP: impact on expression rates of Fas, Bcl‐2 and Bax, the ratio of lymphocyte, killing activity of NK cell, IFN‐γ, TNF, phagocytic ability and IL‐2 (B) Antitumour mechanisms of PCP: impact on IFN‐γ, TNF, phagocytic ability, IL‐6, TPK in cytoplasm and cytomembrane, PTPP in cytoplasm and cytomembrane (C) Antitumour mechanisms of PCP: impact on phagocytic ability, thymus index, spleen index and IFN‐r (D) Antitumour mechanisms of PCP: impact on haemolysin, IL‐4, IgA in serum, IgG in serum and IgM in serum. The gene discussed is IFNG; the disease is pneumocystosis.