Compared with the control group, PCP was able to significantly increase serum levels of total protein (p < 0.05), albumin (p < 0.05), glucose (p < 0.05), total antioxidant capacity (p < 0.05), catalase (p < 0.05), glutathione peroxidase (p < 0.01), Immunoglobulin A (p < 0.05), Immunoglobulin G (p < 0.001), Immunoglobulin M (p < 0.01), and Interleukin-10 (p < 0.01), and down-regulate serum levels of total cholesterol (p < 0.05), triglyceride (p < 0.05), malondialdehyde (p < 0.01), Interleukin-6 (p < 0.05), diamine oxidase, D-lactate, and endotoxin (p < 0.05). The gene discussed is CAT; the disease is pneumocystosis.