Quantitation of HLA-DR expression by cells involved in the skin lesions of tuberculoid and lepromatous leprosy.

A method is described which can be used to quantitate class II MHC antigens (HLA-DR) expressed by cells within tissue sections. A mouse anti-human HLA-DR monoclonal antibody is directly conjugated to the fungal enzyme glucose oxidase. The enzyme, in the presence of its substrate can be used to reduce tetrazolium salts to insoluble coloured formazans. The coloured reaction product is proportional to the amount of antigen and can be eluted from cells and measured spectrophotometrically. The application of this technique to a study of the expression of HLA-DR antigens, functionally significant molecules, by mononuclear cells in the cutaneous lesions of leprosy, is described. When a quantitative measure of the HLA-DR expression was related to the area of the granulomata, significant differences in the HLA-DR expression by cells in the infiltrates associated with lesions of tuberculoid and lepromatous leprosy were observed.