Relation between anti-Mycobacterium leprae antibody activity and clinical features in borderline tuberculoid (BT) leprosy.

Antibody activity against Mycobacterium leprae antigen 7 was determined by radioimmunoassay and IgG antibodies against various antigens present in an M. leprae sonicate by a solid phase radioimmunoassay in 77 patients with borderline tuberculoid (BT) leprosy. In both assays there was a wide variation in antibody activity in individual patients although all were diagnosed as having BT leprosy. The median antibody activity was lower in newly diagnosed cases than in patients appearing with active skin lesions or new skin lesions despite dapsone (DDS) treatment of long duration. Further comparison of patients with high and low antibody activity revealed that high antibody activity was significantly correlated statistically with active skin lesions, new skin lesions and neuritis despite DDS treatment of long duration. The reason for variation in antibody activity in newly diagnosed BT leprosy remains unclear, and this patient group is of particular interest for further characterization of the basis for variation in antibody activity in tuberculoid leprosy.