In Vitro Stimulation of Lymphocytes in Leprosy Patients, Healthy Contacts of Leprosy Patients, and Subjects Not Exposed to Leprosy. Comparison of an Antigen Fraction Prepared from Mycobacterium Leprae and Tuberculin-Purified Protein Derivative.

In vitro lymphocyte stimulation was performed on peripheral blood lymphocytes from 48 leprosy patients, 15 healthy contacts of leprosy patients, and 16 normal controls who lived in a leprosy‐free area and who had not been exposed to leprosy. Tuberculin PPD and an antigen fraction, MLW 1, prepared from M. leprae, were used as stimulants. The MLW 1 preparation contained one antibody‐precipitable component when tested in crossed immuno‐electrophoresis against a polyvalent anti‐M. leprae immunoglobulin preparation, namely the ML 7 antigen. MLW 1 induced strong lymphocyte responses in patients with tuberculoid leprosy and healthy contacts of leprosy patients, but only weak or no responses in lepromatous leprosy patients and non‐exposed controls. A marked depression of the response to tuberculin PPD was observed in lepromatous leprosy patients. The specificity of the MLW 1 antigen is discussed, and a new estimator of specific lymphocyte stimulation, the δcpm′, is introduced.