Macrophages as Mediators of Immunosuppression in Murine African Trypanosomiasis

Abstract

African trypanosomes cause serious infections in man and cattle and can escape immune control by two means: (1) by their ability to change their surface glycoprotein coat to which protective antibodies are directed; thus once one wave of parasites has been controlled, further waves of variant trypanosomes with serologically distinct surface antigens arise (Vickerman 1978). (2) By inducing a general immunosuppression which affects antibody responses as well as T-cell-mediated immune responses to the parasite- and to non-parasite-related antigens. Hosts succumb in the long term, either to very heavy parasite loads or to secondary infections to which they become more susceptible through their defective immune function. Once more infected, hosts show impaired responses to vaccination (e.g. Greenwood 1974a; Rurangirwa et al. 1980). Thus immunosuppression is an important feature in this infection and affects the outcome of the disease. Since antigenic variation presents problems for vaccination strategies, it becomes important to understand the basis of immunosuppression.