title: Effector functions of donor-reactive CD8 memory T cells are dependent on ICOS induced during division in cardiac grafts.
abstract: Alloreactive T-cell memory is present in every transplant recipient and endangers graft survival. Even in the absence of known sensitizing exposures, heterologous immunity and homeostatic T-cell proliferation generate 'endogenous' memory T cells with donor-reactivity. We have recently shown that endogenous donor-reactive CD8 memory T cells infiltrate murine cardiac allografts within hours of reperfusion and amplify early posttransplant inflammation by producing IFN-gamma. Here, we have tested the role of ICOS co-stimulation in eliciting effector function from these memory T cells. ICOS is not expressed on the cell surface of circulating CD8 memory T cells but is rapidly upregulated during cell division within the allograft parenchyma. Donor-reactive CD8 memory T-cell infiltration, proliferation and ICOS expression are regulated by donor class I MHC molecule expression. ICOS blockade significantly reduced IFN-gamma production and other proinflammatory functions of the activated CD8 memory T cells. Our data demonstrate that this induction of ICOS expression within peripheral tissues is an important feature of CD8 memory T-cell activation and identify ICOS as a specific target for neutralizing proinflammatory functions of endogenous CD8 memory T cells.
authors.affiliation: Department of Pathology, Case Western Reserve University, Cleveland, OH, USA. ads23@case.edu
authors.forename: A D
authors.initials: AD
authors.lastname: Schenk
authors.forename: V
authors.initials: V
authors.lastname: Gorbacheva
authors.forename: M
authors.initials: M
authors.lastname: Rabant
authors.forename: R L
authors.initials: RL
authors.lastname: Fairchild
authors.forename: A
authors.initials: A
authors.lastname: Valujskikh
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000235:genetics / Q000378:metabolism*; D001854:Bone Marrow Cells / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D005434:Flow Cytometry; D005805:Genes, MHC Class I; D016027:Heart Transplantation; D007156:Immunologic Memory; D060889:Inducible T-Cell Co-Stimulator Protein; D007371:Interferon-gamma / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014019:Tissue Donors; D014184:Transplantation, Homologous
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; C556694:Icos protein, mouse; D060889:Inducible T-Cell Co-Stimulator Protein; D011948:Receptors, Antigen, T-Cell; D007371:Interferon-gamma