Hyaluronate-CD44 interactions can induce murine B-cell activation.
CD44 is a widely distributed cell surface glycoprotein whose principal ligand has been identified as hyaluronic acid (HA), a major component of the extracellular matrix (ECM). Recent studies have demonstrated that activation through CD44 leads to induction of effector function in T cells and macrophages. In the current study, we investigated whether HA or monoclonal antibodies (MoAbs) against CD44 would induce a proliferative response in mouse lymphocytes. Spleen cells from normal and nude, but not severe combined immunodeficient mice, exhibited strong proliferative responsiveness to stimulation with soluble HA or anti-CD44 MoAbs. Furthermore, purified B cells, but not T cells, were found to respond to HA. HA was unable to stimulate T cells even in the presence of antigen presenting cells (APC) and was unable to act as a costimulus in the presence of mitogenic or submitogenic concentrations of anti-CD3 MoAbs. In contrast, stimulation of B cells with HA in vitro, led to B-cell differentiation as measured by production of IgM antibodies in addition to increased expression of CD44 and decreased levels of CD45R. The fact that the B cells were responding directly to HA through its binding to CD44 and not to any contaminants or endotoxins was demonstrated by the fact that F(ab)2 fragments of anti-CD44 MoAbs or soluble CD44 fusion proteins could significantly inhibit the HA-induced proliferation of B cells. Also, HA-induced proliferation of B cells was not affected by the addition of polymixin B, and B cells from lipopolysaccharide (LPS)-unresponsive C3H/HeJ strain responded strongly to stimulation with HA. Furthermore, HA, but not chondroitin-sulfate, another major component of the ECM, induced B-cell activation. It was also noted that injection of HA intraperitoneally, triggered splenic B cell proliferation in vivo. Together, the current study demonstrates that interaction between HA and CD44 can regulate murine B-cell effector functions and that such interactions may play a critical role during normal or autoimmune responsiveness of B cells.
Rafi
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Department of Biology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
Nagarkatti
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Nagarkatti
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D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D001402:B-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D005109:Extracellular Matrix / Q000502:physiology; D005260:Female; D018960:Hyaluronan Receptors / Q000276:immunology / Q000502:physiology*; D006820:Hyaluronic Acid / Q000494:pharmacology*; D007075:Immunoglobulin M / Q000096:biosynthesis; D017493:Leukocyte Common Antigens / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D015398:Signal Transduction
D000911:Antibodies, Monoclonal; D018960:Hyaluronan Receptors; D007075:Immunoglobulin M; D008070:Lipopolysaccharides; D011993:Recombinant Fusion Proteins; D006820:Hyaluronic Acid; D017493:Leukocyte Common Antigens