Development of specific in vitro lymphocyte responses in cattle infected with Mycobacterium bovis and with Mycobacterium avium.

Two calves infected with Mycobacterium avium and another 2 with Mycobacterium bovis were studied for development and specificity of lymphocyte activation responses and skin reactivity to purified protein derivatives (PPD). Lymphocytes cultured in vitro from infected calves manifested significant uptake of tritiated thymidine in response to the PPD prepared from the homologous organisms, whereas heterologous PPD produced little or no stimulation. The time of appearance of specifically sensitized lymphocytes was studied, as was the specificity of skin reactivity.