CD45 isoform expression during T cell development in the thymus

Eur J Immunol. 1992 Jul;22(7):1843-50. doi: 10.1002/eji.1830220725.


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.

MeSH terms

  • Antigens, CD / analysis*
  • Antigens, CD19
  • Antigens, Differentiation, B-Lymphocyte / analysis
  • Antigens, Differentiation, T-Lymphocyte / analysis
  • Bone Marrow / immunology
  • CD3 Complex
  • CD4 Antigens / analysis
  • CD8 Antigens / analysis
  • Cell Cycle
  • Fetal Blood / immunology
  • Flow Cytometry
  • Histocompatibility Antigens / analysis*
  • Humans
  • Leukocyte Common Antigens
  • Receptors, Antigen, T-Cell / analysis
  • T-Lymphocytes / immunology*
  • T-Lymphocytes / physiology
  • Thymus Gland / immunology*


  • Antigens, CD
  • Antigens, CD19
  • Antigens, Differentiation, B-Lymphocyte
  • Antigens, Differentiation, T-Lymphocyte
  • CD3 Complex
  • CD4 Antigens
  • CD8 Antigens
  • Histocompatibility Antigens
  • Receptors, Antigen, T-Cell
  • Leukocyte Common Antigens