Immunology of parasitic infections

Most parasites, by the nature of their continuous contact with the immune system, generate a prolific immune response. Unfortunately, much of this response is not protective, and some is harmful. Protective immunity in some infections is due to a combination of humoral and cellular immunity; in this circumstance parasites are coated with antibody which makes them susceptible to direct cytotoxicity by macrophages, eosinophils, and neutrophils. Antibody alone is protective against some other infections. Nonspecific and genetic factors are clearly important but are still undefined participants in the host response. The immune response may be pathogenic by inducing hypersensitivity, immunologically mediated fibrosis, or circulating immune complexes. Additionally, parasites have evolved unique ways of protecting themselves from the immune system, including altering their antigenic coat and inducing immunosuppression. Attempts to isolate "host-protective" antigens in parasitic infections may lead to effective vaccine development.