An approach to study in vitro the expression of HLA-encoded genetic factors predisposing to tuberculoid leprosy.

The existence of HLA-encoded genetic factors controlling susceptibility to tuberculoid leprosy in humans has been firmly established. Furthermore HLA-DR2 has been recognized as a marker for tuberculoid leprosy in India. At this moment, however, the gene products involved and the mechanism by which they confer susceptibility to tuberculoid leprosy remain only speculative. In an attempt to detect in vitro the expression of these HLA-encoded factors, we studied 12 tuberculoid leprosy patients and 22 healthy family members in a lymphocyte transformation test (LTT). All individuals were derived from multi-case Indian families, previously reported to show the presence of HLA-linked susceptibility genes. Although the responder-status of the healthy contact siblings was shown to behave independently from the fact whether they were HLA-identical with the patient-siblings or not, some evidence for in vitro expression of HLA-DR2 associated factors could be obtained. Nevertheless, it is concluded that the standard LTT seems not to be a test-system of first choice to detect the in vitro expression of the genes under study.