Changes in HLA-DR antigen expression on cultured human melanoma cells during theophylline treatment

Two human malignant melanoma cell lines, differing in their patterns of HLA-DR antigen expression, were examined for changes in antigen expression following theophylline treatment. In one line, the basal HLA-DR antigen content of which remained constant during culture, theophylline decreased HLA-DR expression, accompanied by morphological changes indicating increased differentiation. In the second line, the surface HLA-DR antigen expression decreased with time during culture and showed no decrease in antigen expression or morphological changes when cultured in the presence of theophylline.