Immunohistological studies of skin biopsies from patients with lepromatous leprosy

Forty-six skin biopsies from lepromatous leprosy patients were examined for immunoglobulin and complement deposits as well as mycobacterial antigens. Rabbit anti-human immunoglobulin, rabbit anti-human C3, and rabbit anti-Mycobacterium bovis (BCG) were used as the primary antigen-detecting antibodies in a peroxidase antiperoxidase technique. Of the 26 biopsies from active erythema nodosum leprosum lesions, 6 were positive for immunoglobulin or complement deposits. These deposits were found in the dermoepidermal junction, within the foamy cells, and, in one patient, around a blood vessel. Five of twenty patients with lepromatous leprosy without erythema nodosum leprosum showed similar deposits in the dermoepidermal junction and within foamy cells. None of these patients had these deposits around blood vessels. Mycobacterial antigens were seen in all biopsies studied. The presence of acute inflammatory infiltrates did not correlate with the presence or absence of immunoglobulin or complement deposits. It is felt that immunoglobulin or complement deposits are not a constant feature of early erythema nodosum leprosum lesions and that these deposits may be secondary rather than primary in these lesions.