Immunohistological analysis of in situ expression of mycobacterial antigens in skin lesions of leprosy patients across the histopathological spectrum- Association of mycobacterial lipoarabinomannan (LAM) and Mycobacterium leprae phenolic glycolipid-I (PGL-I) with leprosy reactions

The presence of mycobacterial antigens in leprosy skin lesions was studied by immunohistological methods using monoclonal antibodies (MAbs) to Mycobac terium leprae-specific phenolic glycolipid I (PGL-I) and to cross-reactive mycobacterial antigens of 36 kd, 65 kd, and lipoarabinomannan (LAM), The st aining patterns with MAb to 36 kd and 65 kd were heterogeneous and were als o seen in the lesions of other skin diseases, The in situ staining of PGL-I and LAM was seen only in leprosy. Both antigens were abundantly present in infiltrating macrophages in the lesions of untreated multibacillary (MB) p atients, whereas only PGL-I was occasionally seen in scattered macrophages in untreated paucibacillary lesions. During treatment, clearance of PGL-I f rom granulomas in IMB lesions occurred before that of LAM, although the for mer persisted in scattered macrophages in some treated patients. This persi stence of PGL-I in the lesions paralleled high serum anti-PGL-I antibody ti ters but was not indicative for the presence of viable bacilli in the lesio ns. Interestingly, we also observed a differential expression pattern of PG L-I and LAM in the lesions of MB patients with reactions during the course of the disease as compared with those without reactions. In conclusion, the in situ expression pattern of PGL-I and LAM in MB patients may assist in e arly diagnosis of reactions versus relapse.