Prothymosin-alpha enhances HLA-DR antigen expression on monocytes from patients with multiple sclerosis.

Monocytes from patients with multiple sclerosis (MS) express decreased numbers of class II major histocompatibility complex (MHC) antigens in peripheral blood and are poor stimulators in the autologous mixed lymphocyte reaction (autoMLR). We assessed the effect of prothymosin-alpha (ProT alpha) on the expression of MHC class II antigens by monocytes. Immediately after isolation, monocytes were analyzed for MHC class II antigen expression using a radiolabelled monoclonal antibody specific for a monomorphic determinant on HLA-DR antigens. After incubation with ProT alpha we observed significant increases in HLA-DR antigens on MS monocytes (1.5- to 4-fold increase compared to freshly isolated monocytes). Kinetic analysis revealed that enhancement peaked after 2 days of incubation with ProT alpha. The increase in HLA-DR antigen on MS monocytes resulted in the restoration of the deficient autoMLR in MS patients. This is the first demonstration suggesting a link between HLA-DR antigen expression and cellular immune defects in MS. The significance of low autoMLR responses for T suppressor levels in MS patients is discussed.