Circulating T-cell numbers and their mitogenic potential in leprosy--correlation with mycobacterial load.

The effect of treatment and mycobacterial load on circulating T-cell numbers and their functional ability was investigated in forty-one patients with leprosy. Both early binding T cells and their responses to phytohaemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) were profoundly and uniformly depressed in untreated, and partially treated, bacilleferous lepromatous leprosy (LL) patients as compared with normal subjects and tuberculoid patients. On elimination of mycobacteria, subsequent to chemotherapy, LL patients regain normality in T-cell numbers and their functions. On the other hand, the specific response of lymphocytes to M. leprae did not alter with decrease in mycobacterial load. It appears that the decrease in T-cell numbers and the deficit in their mitogenic potential is a secondary consequence of disease and is related to the antigenic load in patients with lepromatous leprosy.