title: CD45 isoform expression during T cell development in the thymus.
abstract: Various isoforms of leukocyte common antigen, or CD45, are expressed differentially on T cells at different stages of development and activation. We report studies on CD45 isoform expression on various subsets of human T cells using two- and three-color flow cytometry and cell depletion. Bone marrow cells that were depleted of CD3+ and HLA-DR+ cells were CD45RA-RO-. The earliest CD3-CD4-CD8-CD19- thymocytes were CD45RO- with 20%-30% CD45RA+ cells. The most prominent population of CD4+CD8+ double-positive thymocytes were CD45RA-RO+. Even the CD4+CD8+ blasts were greater than 90% CD45RO+. About 80% of single-positive thymocytes (CD4+CD8- or CD4-CD8+) were also CD45RO+. Only 4.3% of CD4+ and 18% of CD8+ single-positive thymocytes were CD45RA+. In contrast, cord blood T cells which represent the stage that immediately follows single-positive thymocytes, contained 90% CD45RA+ cells. Thus, in terms of CD45 isoform expression, single-positive thymocytes are more like double-positive cells than cord blood T cells. These results suggest the following sequence of CD45 isoform switching during T cell development: CD45RA-RO- or RA+RO- (double-negative thymocytes)----RA-RO+ (double-positive and most single-positive thymocytes)----RA+RO- (cord blood T cells), the last switch from CD45RO to CD45RA occurring as a final step of maturation in the thymus.
authors.affiliation: First Department of Surgery, Osaka University Medical School, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Fujii
authors.forename: M
authors.initials: M
authors.lastname: Okumura
authors.forename: K
authors.initials: K
authors.lastname: Inada
authors.forename: K
authors.initials: K
authors.lastname: Nakahara
authors.forename: H
authors.initials: H
authors.lastname: Matsuda
mesh_terms: D015703:Antigens, CD / Q000032:analysis*; D018941:Antigens, CD19; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D001853:Bone Marrow / Q000276:immunology; D017252:CD3 Complex; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens / Q000032:analysis; D002453:Cell Cycle; D005312:Fetal Blood / Q000276:immunology; D005434:Flow Cytometry; D006649:Histocompatibility Antigens / Q000032:analysis*; D006801:Humans; D017493:Leukocyte Common Antigens; D011948:Receptors, Antigen, T-Cell / Q000032:analysis; D013601:T-Lymphocytes / Q000276:immunology* / Q000502:physiology; D013950:Thymus Gland / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D018941:Antigens, CD19; D000944:Antigens, Differentiation, B-Lymphocyte; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D015704:CD4 Antigens; D016827:CD8 Antigens; D006649:Histocompatibility Antigens; D011948:Receptors, Antigen, T-Cell; D017493:Leukocyte Common Antigens