title: Differential expression of granzymes A and B in human cytotoxic lymphocyte subsets and T regulatory cells.
abstract: Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells use the perforin/granzyme pathway as a major mechanism to kill pathogen-containing cells and tumor cells.(1,2) Dysregulation of this pathway results in several human diseases, such as hemophagocytic lymphohistiocytosis. Here we characterize the single-cell expression pattern of granzymes A and B in human lymphocytes using a flow cytometry-based assay. We demonstrate that most circulating CD56(+)8(-) NK cells, and approximately half of circulating CD8(+) T lymphocytes, coexpressed both granzymes A and B. In contrast, few circulating CD4(+) T lymphocytes expressed granzymes A or B. Activation of CD8(+) T lymphocytes with concanavalin A (ConA)/interleukin-2 (IL-2), and activation of CD4(+) T lymphocytes with antibodies to CD3/CD28 or CD3/CD46 (to generate T regulatory [Tr1] cells), induced substantial expression of granzyme B, but not granzyme A. Naive CD4(+)CD45RA(+) cells stimulated with antibodies to CD3/CD46 strongly expressed granzyme B, while CD3/CD28 stimulation was ineffective. Finally, we show that granzyme B-expressing CD4(+) Tr1 cells are capable of killing target cells in a perforin-dependent, but major histocompatibility complex (MHC)/T-cell receptor (TCR)-independent, manner. Our results demonstrate discordant expression of granzymes A and B in human lymphocyte subsets and T regulatory cells, which suggests that different granzymes may play unique roles in immune system responses and regulation.
authors.affiliation: Department of Pediatrics, Division of Hematology/Oncology, St Louis Children's Hospital, St Louis, MO, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Grossman
authors.forename: James W
authors.initials: JW
authors.lastname: Verbsky
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Tollefsen
authors.forename: Claudia
authors.initials: C
authors.lastname: Kemper
authors.forename: John P
authors.initials: JP
authors.lastname: Atkinson
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Ley
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000276:immunology*; D053804:Granzymes; D006801:Humans; D007694:Killer Cells, Natural / Q000737:chemistry / Q000378:metabolism; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins; D051379:Mice; D018345:Mice, Knockout; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D012697:Serine Endopeptidases / Q000096:biosynthesis* / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000737:chemistry / Q000378:metabolism*; D013602:T-Lymphocytes, Cytotoxic / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D054353:Perforin; C509213:GZMB protein, human; D053804:Granzymes; C509214:Gzmb protein, mouse; D012697:Serine Endopeptidases; C509212:GZMA protein, human