The in vitro response to mitogens of leucocytes from cattle infected with Trypanosoma congolense.

The in vitro proliferative response of bovine leucocytes from peripheral blood to LPS, PWM and Con A was monitored during the course of infection with T. congolense. The stimulatory effect of LPS and PWM on PBL was significantly decreased in infected cattle while the reduction of stimulatory response to Con A was less marked. There was a high background proliferation of unstimulated leucocytes from infected cattle. This increase in background counts correlated with the parasitaemia in that both features were abolished by treatment with the trypanocidal drug Berenil (4,4'-diamidino-diazoaminobenzene-diacetamide acetone). Co-cultivation of trypanosomes with PBL from normal cattle did not depress the responses of the latter to mitogens, and trypanosomes maintained in a cell-free medium failed to incorporate 14C-thymidine under the conditions used.