title: Developmentally regulated expression of P-glycoprotein (multidrug resistance) activity in mouse thymocytes.
abstract: P-glycoprotein (P-gly) is the transmembrane efflux pump responsible for multidrug resistance in tumor cells. The activity of P-gly in mature peripheral lymphocytes is lineage specific, with CD8+ T cells and natural killer (NK) cells expressing high levels as compared to CD4+ T cells and B cells. We have now investigated P-gly activity in immature and mature subsets of mouse thymocytes. Our data indicate that P-gly activity is undetectable in immature CD4-8- and CD4+8+ thymocyte subsets. Among mature thymocytes, P-gly activity is absent in the CD4+ subset but present in the more mature (HSAlow) fraction of CD8+ cells. Furthermore, while thymic CD4-8- T cell receptor (TCR) gamma delta cells have little P-gly activity, a minor subset of CD4-8- or CD4+ TCR alpha beta + thymocytes bearing the NK1.1 surface marker expresses high levels of P-gly activity. Collectively, our results indicate that P-gly activity arises late during thymus development and is expressed in a lineage-specific fashion.
authors.affiliation: Ludwig Institute for Cancer Research, Lausanne Branch, University of Lausanne, Epalinges, Switzerland.
authors.forename: H R
authors.initials: HR
authors.lastname: MacDonald
authors.forename: U
authors.initials: U
authors.lastname: Bommhardt
authors.forename: J C
authors.initials: JC
authors.lastname: Cerottini
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D002454:Cell Differentiation; D018432:Drug Resistance, Multiple / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D008198:Lymph Nodes / Q000166:cytology / Q000254:growth & development; D051379:Mice; D008810:Mice, Inbred C57BL; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000032:analysis; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000032:analysis; D016176:T-Lymphocyte Subsets / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology / Q000254:growth & development*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta