Cellular immunity in patients with leprosy. Circulating T lymphocytes and their response to PHA in leprosy.

The ability of peripheral blood lymphocytes from polar lepromatous (LL), borderline lepromatous (BL) and borderline tuberculoid (BT) patients to transform in vitro in the presence of phytohemagglutinin was found to be significantly reduced. A significant reduction in the percentage and absolute number of T lymphocytes was observed in LL cases. In BL cases the number of T lymphocytes was decreased, but the reduction was proportional to the reduction in the total lymphocyte population was observed only in bacteriologically positive cases.