Differential surface expression of HLA-DRB1 and HLA-DRB4 among peripheral blood cells of DR4 positive individuals.

Increasing interest in the functional consequences of differential expression of MHC class II molecules prompted us to examine the surface expression of HLA class II molecules on fresh peripheral blood mononuclear cells. Differential regulation of DR4 and DRB4 was shown for peripheral blood monocytes. In addition, DR4 expression is upregulated on B cells of patients suffering from chronic inflammation and is reduced under prednisolone-treatment. The expression levels of total DR molecules on a given cell type are almost identical comparing different haplotypes among non-RA controls, suggesting that the alpha-chain determines the level of surface expression. The present findings fit the hypothesis that the differential expression of HLA class II molecules is involved in regulation of the immune response and may thus contribute to determining susceptibility to immunological diseases.