Signal transduction by HLA class II antigens expressed on activated T cells

✍ Scribed by Niels Ødum; Paul J. Martin; Gary L. Schieven; John A. Hansen; Jeffrey A. Ledbetter

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 805 KB
• Volume: 21
• Category: Article
• ISSN: 0014-2980
• DOI: 10.1002/eji.1830210119

✦ Synopsis

Human T cells express HLA class I1 antigens upon activation. Although activated, class II+ Tcells can present alloantigens under certain circumstances, the functional role of class I1 antigens on activated T cells remains largely unknown. Here, we report that cross-linking of HLA-DR molecules expressed on allospecific, CD4+ Tclones and cell lines can function as transduction elements that trigger rapid cellular responses including tyrosine phosphorylation of cellular proteins and mobilization of Ca2+ from internal stores. The proteins phosphorylated on tyrosine were distinct from those observed after cross-linking CD4.

Ligation of CD4 and class I1 molecules generated a synergistic effect of the intracellular free Ca2+ concentration response that required an interaction between the molecules on the cell surface. Since class I1 is the natural ligand for CD4, the present data suggest that class I1 is induced on activated T cells to regulate CD4 function, possibly by specific interaction with the CD4-associated p56ICk protein tyrosine kinase.