Trypanosoma congolense: Specific transformation in vitro of leukocytes from infected or immunized cattle

An assay to measure the specific proliferation in vitro of peripheral blood leukocytes (PBL) in response to ultrasonicated trypanosomes was adapted for use in cattle. The kinetics of mitosis exhibited by PBL from cattle which had been treated following infection with Trypanosoma congolense paralleled the development of a delayed-type skin reaction elicited with ultrasonicated and Formalin-fixed T. congolense. Responses in both tests were maximal on the fourth day after initiation. Specific proliferation of PBL harvested from cattle which had been immunized with intact, nonviable trypanosomes was also elicited in vitro by trypanosomal antigen. Peripheral blood leukocytes taken from cattle immunized with 50 μg of variant-specific surface antigen (VSSA) from T. brucei and from cattle infected with T. congolense were not stimulated to divide in vitro by ultrasonicated trypanosomes.