The nature of immunosuppression in Trypanosoma brucei infections in mice. II. The role of the T and B lymphocytes.

In an investigation of the immunosuppression associated with trypanosomiasis, the thymus-derived lymphocytes (T cells) and the thymus-independent lymphocytes (B cells) in mice with subacute infections were studied. It was shown that: (a) there was a massive plasma cell response in lymph nodes and spleen which replaced the thymus-dependent areas; (b) a failure of antibody production at the cellular level occurred as shown by the absence of IgM PFC responses to SRBC and lipopolysaccharide; (c) T cells appeared relatively normal as judged by their ability to proliferate following a primary stimulus with oxazolone unless measured during the terminal stages of the disease; (d) immune competence was rapidly restored after treatment with a trypanocidal drug. It appeared that immunosuppression was closely associated with the presence of living trypanosomes, possibly mediated through a B-cell defect. The mechanism whereby this might occur is discussed.