An immunoperoxidase study of immunological factors in skin lesions across the spectrum of leprosy.

The immunoperoxidase technique was used to assess the quantity and situation of various immunological factors in 24 skin biopsies which represented the leprosy spectrum from TT to LL. The factors were immunoglobulins (IgG and IgM), complement components (C3, C3d and Clq), plasminogen, muramidase (lysozyme), C-reactive protein and alpha-1-antitrypsin. The results were compared with previous reports on the assessment of these factors in serum. The quantities of these factors in the lesions produced peaks at TT and LL, with a dip in the BT-BB region (C-reactive protein and alpha-1-antitrypsin excepted). The immunoglobulins, present mainly in plasma cells and lymphocytes, correlated in general with reports of serum levels. The complement components were present in appreciable amounts, though the serum levels are depressed; they were seen in young mononuclear cells with a low bacterial load. All factors produced an ascending gradient in active lesions from BT to BL or LL, which correlated with the bacterial load and its viability. In regression (studied only in LL) there was a decrease in all factors. In TT there was an increase in most factors which did not correlate with the antigen load, and which probably resulted in an excess of antibody over antigen. In active LL there is probably an antigen excess. The results suggest the possibility that there is a common defect from BT to LL, in which the generation of immunological factors within the lesion of immunological factors within the lesion is a secondary response to the antigenic load. In TT alone (a rare group) is there an enhanced immunological response unrelated to the antigen load. In support of this was the finding of Ia antigen only in TT lesions.