Characteristics of monoclonal antibodies against HLA antigens class II. M. A. Kryzhanova, A. Yu. Baryshnikov, E. A. Frolova, V. V. Novikov. Research Institute of Epidemiology and Microbiology, Nizhny Novgorod, Russia; Cancer Research Center, Moscow, Russia, A number of monoclonal antibodies of ICO series interacting with HLA antigens class II have been studied for specificity. It is shown that monoclonal antibodies ICO-1, ICO-2 and ICO-8 are directed against common determinant of HLA-DR antigens, whereas monoclonal antibodies ICO-15.5 interact with class II antigens unrelated to HLA-DR antigens.