The in situ characteristics of mononuclear cell infiltrates in dermal lesions of leprosy.

The in situ nature of mononuclear cell infiltrates in the dermal lesions of 38 untreated leprosy patients was studied by means of conventional surface marker techniques using erythrocytes coated with AET, anti-erythrocyte IgG antibody, hemolysin and complement for the identification of T cells, and cells bearing Fc and C3 receptors, respectively. In general, T cells were the predominant lymphocytes in the leprosy lesions. They were mostly seen to be associated with epithelioid cell granulomas and showed maximal density in tuberculoid leprosy. A graded reduction of T cells was observed in borderline leprosy with a severe reduction/absence in polar lepromatous leprosy. The cells of the mononuclear phagocyte series in the various granulomas of the leprosy spectrum showed the presence of Fc and C3 receptors. Cells bearing a higher density of these receptors had a peripheral localization; whereas cells showing diffuse staining for nonspecific esterase were located more in the central regions of the granulomas. The differences in the individual cells of the phagocytic series appeared to be related to cell maturity; whereas the quantity of T cell infiltration in the lesions showed a correlation with the leprosy spectrum.