In vitro lymphocyte response to purified protein derivative, BCG, and Mycobacterium leprae in a population not exposed to leprosy

Abstract

Lymphocytes from 14 BCG vaccinated donors, seven tuberculin positive and seven tuberculin negative by skin testing, were stimulated in vitro with four mycobacterial antigens, purified proteins derivative (PPD), PPD/BCG, whole BCG bacilli, and whole Mycobacterium leprae and also with Candida antigen and phytohemagglutinin. The response was measured by incorporation of 3H labeled thymidine. The response to PPD, PPD/BCG, and BCG was found to correlate with the result of skin testing with tuberculin. The tuberculin positive group also responded more strongly to M. leprae, whereas the two groups did not differ significantly in their response to Candida antigen or phytohemagglutinin. These findings indicate a certain degree of cross reactivity between BCG and M. leprae. The use of the lymphocyte transformation test to measure antigenic cross reactivity is discussed.