Human recombinant interferon α-2C enhances the expression of class II HLA antigens on hairy cells

Isolated splenic hairy cells from three untreated patients were cultured in presence of recombinant human interferon alpha-2C (IFNα). Ultrastructural cytochemistry and immunophenotype analysis with a large panel of monoclonal antibodies were performed to study cellular modification induced by IFNα. Hairy cells showed a typical phenotype: SmIg+, B1+, BA1(±), anti-Tac+, OKDR+, Leu-M5+, HC2+, TRAP+, myeloperoxidase-. Under our experimental conditions, we found no direct cytotoxic effects or significant variations in morphology, cytochemistry, and percentage of reactivity with the tested monoclonal antibodies. After culturing in the presence of different doses of IFNα, we observed a significant enhancement of the expression of class II HLA antigens as demonstrated by increased fluorescence for OKDR, OKIa, Leu-10 at fluorescence-activated cell sorting analysis. In agreement with this finding IFNα-treated hairy cells showed an increased stimulatory capacity v allogeneic T cells in one-way mixed lymphocyte reaction. To our knowledge this is the first report describing the induction of class II HLA antigens on hairy cells by IFNα.