Trypanosoma gambiense: immunosuppression and polyclonal B-cell activation in mice

The relationship between the suppression of antibody response and polyclonal B-cell activation was studied in mice treated with a cell homogenate of Trypanosoma gambiense. The cell homogenate injection in mice caused a progressive increase in splenic background plaque-forming cell response to sheep erythrocyte. In the mice with markedly increased background plaque-forming cell response, the different reactivity in the primary antibody response to sheep erythrocytes was observed between the intraperitoneal and intravenous immunization with sheep erythrocytes. The intraperitoneal immunization of mice with sheep erythrocytes strongly suppressed the antibody response, while the intravenous immunization with sheep erythrocytes led to an enhancement of the antibody response. The intraperitoneal injection of silica particles, a toxic agent to macrophages, 30 min before intraperitoneal immunization with sheep erythrocytes abolished the suppression of the antibody response completely. In addition, restoration of the suppressed antibody response was found in mice immunized intraperitoneally with a high dose of sheep erythrocytes. It appears that the suppression of antibody response is not attributable to polyclonal B-cell activation, and is associated with the elevation of the phagocytic activity of peritoneal macrophages.