What is the Pathogenic Mechanism of Cryptococcus Neoformans?

The pathogenic mechanism of Cryptococcus neoformans is that the capsular polysaccharide in the bacteria inhibits the immune function of the body and increases immune tolerance. Capsular polysaccharide can inhibit the phagocytosis of neutrophils and weaken the immune response of T cells to it. Cryptococcus neoformans is generally exogenous infection, which exists abundantly in bird and pigeon feces. Pigeons are an important source of infection. The main invasion route is the respiratory tract, often causing lung infections. Cryptococcus neoformans can also be found in the normal microbial flora of the human body. Endogenous infections can occur when the immune function of the body is low, such as leukemia, AIDS, and diabetes. Cryptococcus neoformans can also disseminate from the lungs to other parts of the body through the blood, most easily invading the central nervous system, mainly causing subacute and chronic infections of the meninges, with a high fatality rate. It can also disseminate to the skin, mucosa, bones, and internal organs. The genus Cryptococcus includes 17 species and 18 varieties, of which only Cryptococcus neoformans and its varieties are pathogenic, mainly invading the central nervous system. Cryptococcus neoformans is an environmental saprophytic fungus that survives widely in soil and pigeon feces. Normal people are often exposed to environments contaminated with Cryptococcus neoformans, but few develop the disease. When the body's resistance decreases, it is easier for it to invade the body and cause disease. Due to the use of tumor and chemotherapy drugs, the prevalence of AIDS, the use of immunosuppressive drugs after transplantation, and other reasons, the incidence of Cryptococcus neoformans is increasing. It has become a common complication of AIDS patients abroad and an important cause of patient deaths. The incidence of Cryptococcus neoformans in China is also showing an increasing trend year by year.