BETA(2)-MICROGLOBULIN EXPRESSION OF AIDS-RELATED AND CLASSICAL KAPOSIS-SARCOMA

The expression of beta(2)-microglobulin, the invariable light chain of HLA class I molecules, of Kaposi's sarcoma from 11 AIDS patients and from 11 patients without known immunodeficiency was studied by immunoh istochemistry using a polyclonal antibody to beta(2)-microglobulin. Th e staining intensity of spindle cells in these lesions was scored in a semiquantitative system. We found that the spindle cells of Kaposi's sarcomas from AIDS patients showed significantly increased staining in tensity for beta(2)-microglobulin compared to those of Kaposi's sarcom as from non-AIDS patients. The results may indicate that Kaposi's sarc omas developing in immunocompromised individuals, such as AIDS patient s, are not subject to immune selection by T cells eliminating HLA clas s I high-expressing tumor cells, while this may be the case in non-AID S patients. Alternatively, the results may be caused by differences in the activity of cytokines, which upregulate the expression of HLA cla ss I molecules on the cell surface.