Antigen presentation by brain microvessel smooth muscle and endothelium

It has been previously reported that cultured brain microvessel smooth muscle cells (SM) express major histocompatibility complex (MHC) class II antigen. Here we report that SM is able to present ovalbumin (OVA) antigen to an OVA-specific T cell hybridoma (A2.2E10) and also presents keyhole limpet hemocyanin (KLH) to a KLH-specific T cell clone (HDK-1). Both the class II expression and the antigen-presenting capacity of SM cells is increased by interferon-gamma stimulation. Antigen presentation by SM is also MHC restricted as it is blocked by anti-Ia monoclonal antibodies. In contrast to SM, brain endothelium (En) presents whole OVA, digested OVA and KLH poorly, to a much lesser degree than SM, to the same antigen-specific T cells.