title: Expression characteristics and stimulatory functions of CD43 in human CD4+ memory T cells: analysis using a monoclonal antibody to CD43 that has a novel lineage specificity.
abstract: We have used HSCA-2, an mAb that recognizes a sialic acid-dependent epitope on the low molecular mass (approximately 115-kDa) glycoform of CD43 that is expressed in resting T and NK cells, to examine the expression characteristics and stimulatory functions of CD43 in human CD4+ memory T cells. Having previously reported that the memory cells that respond to recall Ags in a CD4+ CD45RO+ T cell population almost all belong to a subset whose surface CD43 expression levels are elevated, we now find that exposing these same memory T cells to HSCA-2 mAb markedly increases their proliferative responsiveness to recall Ags. We think it unlikely that this increase in responsiveness is a result of CD43-mediated monocyte activation, especially given that the HSCA-2 mAb differs from all previously used CD43 mAbs in having no obvious binding specificity for monocyte CD43. Predictably, treatment with HSCA-2 mAb did not lead to significant recall responses in CD4+ CD45RO+ T cells, whose CD43 expression levels were similar to or lower than those of naive cells. Other experiments indicated that the HSCA-2 mAb was capable of enhancing the proliferative responsiveness of CD4+ memory T cells that had been exposed to polyclonal stimulation by monocyte-bound CD3 mAb and could also act in synergy with CD28 mAb to enhance the responsiveness of CD4+ T cells to CD3 stimulation. Taken together, these findings suggest that the CD43 molecules expressed on CD4+ memory T cells may be capable of enhancing the costimulatory signaling and hence providing accessory functions to TCR-mediated activation processes.
authors.affiliation: Laboratory of Immunology, Department of Radiobiology/Molecular Epidemiology, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami Ward, Hiroshima 732-0815, Japan. kyoizumi@rerf.or.jp
authors.forename: Seishi
authors.initials: S
authors.lastname: Kyoizumi
authors.forename: Takaaki
authors.initials: T
authors.lastname: Ohara
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Kusunoki
authors.forename: Tomonori
authors.initials: T
authors.lastname: Hayashi
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Koyama
authors.forename: Naohiro
authors.initials: N
authors.lastname: Tsuyama
mesh_terms: D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology*; D018106:CD28 Antigens / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D019070:Cell Lineage / Q000276:immunology; D002478:Cells, Cultured; D006801:Humans; D007156:Immunologic Memory / Q000276:immunology*; D051917:Leukosialin; D008213:Lymphocyte Activation / Q000276:immunology; D009000:Monocytes / Q000276:immunology; D012795:Sialoglycoproteins / Q000235:genetics / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018106:CD28 Antigens; D017252:CD3 Complex; D051917:Leukosialin; C465014:SPN protein, human; D012795:Sialoglycoproteins