Both CD45RA+ and CD45RA- subpopulations of CD8+ T cells contain cells with high levels of lymphocyte function-associated antigen-1 expression, a phenotype of primed T cells.
Expression of CD45 isoforms and some adhesion molecules on T cells change during T cell activation. In CD4+ T cells, it has been reported that CD45RA is lost and CD45RO is up-regulated when CD4+ T cells are stimulated. This change seemed to be irreversible and thus CD45RA may serve as a marker for virgin T cells and CD45R0 as a marker for memory T cells in CD4+ T cells. In CD8+ T cells, however, the expression of CD45 isoform has been less well understood. We have previously reported the switching of CD45 isoform expression may be reversible and CD8+CD45RA+ T cells may contain preactivated T cells. We present further evidence to support this notion by investigating the expression of lymphocyte function-associated Ag (LFA-1) in relation to CD45 isoform expression in various T cell populations in the human. In the thymus and umbilical cord blood, more than 97% of both CD4+ and CD8+ single positive T cells expressed LFA-1 at a low level. In CD4+ peripheral blood T cells, a high level of LFA-1 expression was found only in the CD45RA- population: 98% of CD45RA+ cells were LFA-1low. In CD8+ peripheral blood T cells, in contrast, a distinct population of LFA-1high cells was found in CD45RA+ subset, comprising about 45% of this subset in a 32-yr-old donor. In 7 days after stimulation with PHA, all CD4+ and CD8+ T cells, irrespective of their CD45 isoform expression, were LFA-1high. The proportion of CD45RA+ cells decreased in CD4+ but slightly increased in CD8+ T cells after the stimulation. These results support the notion that CD45RA and CD45R0 mark virgin and memory T cells respectively in the CD4+ T cells, and that CD8+CD45RA- T cells are primed. However, the validity of CD45RA as a marker of virgin cells in CD8+ T cells is seriously questioned.
Okumura
M
M
First Department of Surgery, Osaka University Medical School, Japan.
Fujii
Y
Y
Inada
K
K
Nakahara
K
K
Matsuda
H
H
D000328:Adult; D015703:Antigens, CD / Q000032:analysis; D015704:CD4 Antigens / Q000032:analysis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D016827:CD8 Antigens / Q000032:analysis*; D002478:Cells, Cultured; D005434:Flow Cytometry; D006801:Humans; D019012:Integrin beta1; D017493:Leukocyte Common Antigens / Q000032:analysis*; D008213:Lymphocyte Activation; D016169:Lymphocyte Function-Associated Antigen-1 / Q000032:analysis*; D016176:T-Lymphocyte Subsets / Q000276:immunology*
D015703:Antigens, CD; D015704:CD4 Antigens; D016827:CD8 Antigens; D019012:Integrin beta1; D016169:Lymphocyte Function-Associated Antigen-1; D017493:Leukocyte Common Antigens