title: Loss of CD45R (Lp220) represents a post-thymic T cell differentiation event.
abstract: CD45R+ and CDw29+ CD4+ T cells are widely regarded as separate functionally defined T cell lineages. The work described here indicates that they represent maturation stages within the same differentiation pathway. Purified populations of CD4+ or CD8+ T cells, after stimulation with PHA, lose cell surface expression of CD45R (Lp220) and gain an increased surface density of CDw29 (4B4). Clonal analysis demonstrated that individual CD4+ CD45R+ T cells lost CD45R and acquired CDw29 with time in culture. This effect was selective for the high Mr 220-kDa form of the T200 (CD45) complex because the density of CD45, detected by an antibody to common determinants, did not decrease. This strongly indicates that CD45R+ cells are an immature stage in a lineage that culminates in CDw29 expression. To further define the expression of CD45R and CDw29, we analyzed infant thymus cells. Thymocytes include only 4 to 6% CD45R+ cells, but 95% express CDw29 in moderate density. The CD45R+ set appears to include mainly single CD4+ or CD8+, CD3 "bright" medullary cells, although only 15 to 25% of thymocytes with medullary phenotype express CD45R. In vitro culture of thymocytes with Con A and T cell growth factor induces expression of CD45R but these cells differ from the peripheral CD45R+ set by virtue of their co-expression of a high density of CDw29 (4B4) Ag. We postulate that post-thymically CD45R (Lp200) and CDw29 (4B4) comprise a functional assembly on the surface of T cells that changes in composition after stimulation with Ag or mitogen. This may result in enhanced ability of an Ag-experienced T cell to respond effectively to Ag due perhaps to a more efficient signaling complex.
authors.affiliation: Department of Immunology, University of Alberta, Edmonton, Canada.
authors.forename: H M
authors.initials: HM
authors.lastname: Serra
authors.forename: J F
authors.initials: JF
authors.lastname: Krowka
authors.forename: J A
authors.initials: JA
authors.lastname: Ledbetter
authors.forename: L M
authors.initials: LM
authors.lastname: Pilarski
mesh_terms: D000943:Antigens, Differentiation / Q000032:analysis* / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis* / Q000276:immunology; D002454:Cell Differentiation; D002469:Cell Separation; D002648:Child; D002999:Clone Cells / Q000032:analysis / Q000145:classification; D006801:Humans; D007223:Infant; D017493:Leukocyte Common Antigens; D008213:Lymphocyte Activation; D010641:Phenotype; D010835:Phytohemagglutinins / Q000494:pharmacology; D013601:T-Lymphocytes / Q000032:analysis / Q000166:cytology* / Q000276:immunology; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D010835:Phytohemagglutinins; D017493:Leukocyte Common Antigens