Microvilli structures on B lymphocytes: inducible functional domains?
2004 (English)In: Int Immunol, ISSN 0953-8178, Vol. 16, no 2, 353-64 p.Article in journal (Refereed) Published
Interactive contact between B lymphocytes and T cells is necessary for their expansion during an immune response. It has been shown that B lymphocytes receive signals from T cells, such as IL-4 and cross-linking of CD40, which are crucial for their differentiation. We previously found that these factors induce formation of microvilli on B cells and that this was correlated with increased homotypic adhesion of B lymphocytes. In this study we have investigated if IL-4 induce segregation of proteins to microvilli and lipid rafts. Using immuno-electron microscopy we analyzed cell-surface distribution of molecules involved in B-T cell co-activation. Recruitment to detergent-resistant membrane fractions was analyzed using sucrose gradient centrifugation. We found that microvilli were enriched in ICAM-1 and MHC class II molecules. In contrast, LFA-1 and CD40 were more abundant on the smooth cell surfaces, while B7-2 (CD86) was randomly distributed. We also discovered that depletion of cholesterol, using beta-methyl-cyclodextrin, lowered the number of microvilli, indicating that intact lipid rafts are required for their expression. Moreover, activation of B lymphocytes by lipopolysaccharide (LPS) induced increased expression of GM(1), a marker for lipid rafts. However, although both surface and total levels of GM(1) were similar in B lymphocytes stimulated with either LPS or LPS plus IL-4, GM(1) was mainly expressed on microvilli in LPS plus IL-4-stimulated cells. Taken together, our results indicate that microvilli represent distinct inducible membrane domains that can regulate direct cell-cell interactions via grouping and three-dimensional presentation of cell-surface receptors.
Place, publisher, year, edition, pages
2004. Vol. 16, no 2, 353-64 p.
Animals, Antigens; CD/metabolism, Antigens; CD40/metabolism, B-Lymphocytes/immunology/*ultrastructure, Cell Communication/drug effects/physiology, Cholera Toxin/pharmacology, Cyclodextrins/pharmacology, Genes; MHC Class II/*physiology, Intercellular Adhesion Molecule-1/*metabolism, Interleukin-4/pharmacology, Lipopolysaccharides/pharmacology, Lymphocyte Activation/drug effects, Lymphocyte Function-Associated Antigen-1/metabolism, Membrane Glycoproteins/metabolism, Membrane Microdomains/metabolism/*ultrastructure, Mice, Microvilli/immunology/*ultrastructure, Research Support; Non-U.S. Gov't, T-Lymphocytes/immunology
IdentifiersURN: urn:nbn:se:uu:diva-73206PubMedID: 14734621OAI: oai:DiVA.org:uu-73206DiVA: diva2:101117