
<ArticleTitle>Signalling via MHC class II molecules modifies the composition of GEMs in APC.</ArticleTitle>
<AbstractText>Major histocompatibility complex (MHC) class II molecules are responsible for peptide presentation to helper T lymphocytes and as such play an essential role in the immune response. These molecules transmit intracellular signals leading to diverse consequences in B lymphocytes including proliferation and apoptosis. Recent studies have revealed that glycolipid enriched membrane microdomains (GEMs) behave as signalling platforms for a variety of lymphocyte receptors. We have quantified human <prot>leucocyte antigen (HLA)-DR</prot> molecules localized in GEMs in human B lymphocytes. Use of a model imitating the interaction of <prot>HLA-DR</prot> with a T-cell receptor (TCR) modified the constituents of the <prot>HLA-DR</prot>-enriched GEMs. Confocal microscopy demonstrated a recruitment of <prot>HLA-DR</prot> and the ganglioside GM1 at the site of <prot>HLA-DR</prot> interaction with the stimulating ligand. Moreover, cholesterol depletion efficiently impaired this recruitment. Co-localizing proteins detected in <prot>HLA-DR</prot>-enriched GEMs include <prot>protein kinase C (<prot>PKC</prot>)-delta</prot> and <prot>actin</prot>. These data reveal that MHC class II antigens are localized in GEMs in mature human B lymphocytes and indicates that the formation of the immunological synapse regulates the composition of <prot>HLA-DR</prot> enriched GEMs in the antigen presenting cell (APC).</AbstractText>
