Lymphocyte transformation test in lepromatous leprosy patients and their healthy siblings.

Lymphoproliferative response to M. leprae, PHA, PPD and mixed leucocyte culture (MLC) were measured in 20 cases of lepromatous leprosy, 17 of their normal healthy siblings and 15 healthy controls. 7 siblings of LL patients were HLA-D identical, which was identified by doing MLC reaction. All healthy siblings including HLA-D identical responded normal to all stimulating agents including M. leprae antigen. In contrast 20 cases of LL responded very poorly to M. leprae antigen and almost near normal to other stimulating agents. The specific unresponsiveness of LL patients to M. leprae antigen does not result from an HLA linked genetic defect and the defective CMI response to M. leprae antigen seems to be acquired and not genetically determined.