Bovine trypanosomiasis: effect on the immune response of the infected host.

Yearling cattle were inoculated with a recently isolated field strain of Trypanosoma congolense. Dinitrophenylated ovalbumin, a bacteriophage, or bovine parainfluenza-3 virus injected into the cattle during the first 5 weeks of infection resulted in peak serum antibody titers lower but not much lower than those produced by noninfected cattle. Primary and secondary antibody responses of inoculated cattle required more time to reach peak titers. Peripheral blood lymphocyte concentrations decreased to 42% of preinfection base-line value 1 1/2 weeks after the onset of T congolense infection and thereafter plateaued at less than 75% of base-line value. Lymphocyte cultures prepared from infected and noninfected cattle gave no marked differences in [(3)H]thymidine uptake after stimulation with phytohemagglutinin or pokeweed mitogen. Differences in lymphpocyte responsiveness were not noticed in one-way mixed lymphocyte culture reactions, using mitomycin C-treated lymphocytes from noninfected cattle as stimulator cells.