title: FCRL6 distinguishes mature cytotoxic lymphocytes and is upregulated in patients with B-cell chronic lymphocytic leukemia.
abstract: Fc receptor-like 6 (FCRL6), the most recently characterized member of the FCRL family, is a cell surface glycoprotein with tyrosine-based regulatory potential. An extensive survey of human hematopoietic tissues disclosed that FCRL6 expression by NK- and T-cell subpopulations increases as a function of differentiation and is remarkably restricted to mature lymphocytes with cytotoxic capability. In particular, FCRL6 distinguishes perforin-expressing CD56dim NK cells, Vdelta1+ and Vdelta2+ gammadelta T cells, effector and effector memory CD8+ T cells, and rare cytotoxic CD4+ T cells in adult tissues. Analysis of this receptor in B-cell chronic lymphocytic leukemia (CLL) was also performed. FCRL6 was found to mark significantly expanded populations of cytotoxic CD8+ T, CD4+ T, and NK cells in patients with CLL. Despite sequence homology with the known Fc receptors for IgG and IgE, FCRL6 did not bind Ig. Although FCRL6 can be tyrosine-phosphorylated, its antibody-mediated ligation was unable to influence cellular activation. Collectively, these results demonstrate that FCRL6 is a distinct indicator of cytotoxic effector lymphocytes that is upregulated in diseases characterized by chronic immune stimulation.
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294-2182, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Schreeder
authors.forename: Jicun
authors.initials: J
authors.lastname: Pan
authors.forename: Fu Jun
authors.initials: FJ
authors.lastname: Li
authors.forename: Eric
authors.initials: E
authors.lastname: Vivier
authors.forename: Randall S
authors.initials: RS
authors.lastname: Davis
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology*; D010766:Phosphorylation; D011956:Receptors, Cell Surface / Q000032:analysis / Q000502:physiology*
chemical_list: C520037:FCRL6 protein, human; D011956:Receptors, Cell Surface