title: Differential expression of CD40 ligand on T cell subsets. Implications for different roles of CD45RA+ and CD45RO+ cells in IgE production.
abstract: Physical contact between human T lymphocytes and B lymphocytes is required for the induction of IgE production. In the present study, we examined the abilities of CD45RA+ and CD45RO+ human T cell subsets to provide help for IgE production by human peripheral blood B cells in the presence of IL-4. Purified peripheral CD45RA+ T cells are much better inducers of IgE synthesis than are CD45RO+ T cells. Activation of CD45RA+ T cells, but not CD45RO+ T cells, via the TCR/CD3 complex is sufficient to confer the ability to provide IgE help, suggesting that an inducible T cell surface molecule plays an important role in this system. The CD40 ligand, an inducible T cell surface molecule, is expressed at higher levels on CD45RA+ T cells as compared with CD45RO+ T cells following CD3-stimulation. Blocking of the CD40-CD40 ligand interaction in vitro by the addition of a soluble form of B cell CD40 Ag completely blocks IgE production induced by CD45RA+ T cells. Finally, the in vitro conversion of CD45RA+ T cells to the CD45RO+ phenotype is accompanied by a loss in the ability of these cells to express the CD40 ligand in response to anti-CD3 stimulation as well as a loss in their ability to provide IgE help. These results suggest that both CD45 subsets may play significant and distinct roles in the induction of IgE production under physiologic conditions: CD45RO+ T cells provide IL-4 and the CD45RA+ subset provides the second signal via the CD40 ligand.
authors.affiliation: Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206, USA.
authors.forename: H R
authors.initials: HR
authors.lastname: Patel
authors.forename: A
authors.initials: A
authors.lastname: Oshiba
authors.forename: J D
authors.initials: JD
authors.lastname: Jeppson
authors.forename: E W
authors.initials: EW
authors.lastname: Gelfand
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology*; D019013:CD40 Antigens / Q000502:physiology; D023201:CD40 Ligand; D002478:Cells, Cultured; D006801:Humans; D007073:Immunoglobulin E / Q000096:biosynthesis*; D016130:Immunophenotyping; D007700:Kinetics; D017493:Leukocyte Common Antigens / Q000032:analysis / Q000502:physiology*; D008024:Ligands; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D016176:T-Lymphocyte Subsets / Q000145:classification / Q000276:immunology / Q000378:metabolism*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D019013:CD40 Antigens; D008024:Ligands; D008562:Membrane Glycoproteins; D023201:CD40 Ligand; D007073:Immunoglobulin E; D017493:Leukocyte Common Antigens