Regulation of the epithelial cell-specific integrin, CD103, by human CD8+ cytolytic T lymphocytes.

BACKGROUND: The destruction of the graft epithelium by CD8+ cytolytic T lymphocytes (CTL) is an important aspect of organ allograft rejection. Our recent finding in a mouse model that the epithelial cell-specific integrin, CD103, defines a subset of CD8+ CTL potentially sheds new light onto such interactions. The goal of the present study was to assess the relevance of these data to the human system. METHODS: CD103 expression by human T-cell populations generated in mixed lymphocyte cultures or isolated from transplant nephrectomy specimens was quantitated using multiparameter FACS analyses. RESULTS: CD103 defined a major subset (26-76%) of CD8+ CTL generated in human mixed lymphocyte cultures; cell sorting experiments confirmed that the CD103+ and CD103- subsets both possess allospecific lytic activity. Anti-transforming growth factor (TGF)-beta blocked the appearance of the CD103+ CTL subset, and persistent expression of CD103 by CD8+ CTL was dependent on bioactive TGF-beta. Isolated CD103+ and CD103- CD8 subsets maintained their phenotypic integrity during in vitro expansion, although optimal CD103 expression on the former was TGF-beta dependent. Although CD103+ cells were rare among activated CD8 cells in peripheral lymphoid compartments (< 10%), analyses of transplant nephrectomy specimens revealed that a major subset (21-61%) of CD8 memory/effector cells that infiltrate rejecting renal allografts express high levels of CD103. CONCLUSIONS: We conclude that CD103 defines a discrete and stable subset of human CD8+ CTL and that CD103 expression by such cells is initiated and maintained by bioactive TGF-beta. These data point to the existence of a human effector subset that is uniquely specialized for the destruction of the graft epithelium.

Integrin-mediated interactions influence the tissue specificity of CD8+ cytolytic T lymphocytes.

We previously reported that CD8+ cytotoxic T lymphocytes (CTL) elicited in response to allogeneic renal epithelial cells (anti-REC CTL) preferentially lyse REC targets as compared to conventional lymphoid cell (LC) targets. It is often tacitly assumed that such cell type specificity results from CTL recognition of tissue-restricted MHC/peptide complexes. However, we herein report that anti-REC CTL uniquely express CD103, an integrin with known specificity for the epithelial cell-restricted ligand E-cadherin, and are deficient in expression of CD11a (LFA-1), an integrin known to play a critical accessory role in promoting lysis of LC targets. We demonstrate that CD8+ CTL clones with disparate CD103/CD11a phenotypes but identical specificities for allo-MHC/peptide can exhibit marked differences in cell type specificity. Antibody blocking studies provided direct evidence that CD103 serves as an accessory molecule that promotes lysis of REC targets. Taken together, these data indicate that integrin-mediated accessory interactions can influence the capacity of CD8+ CTL to discriminate between different cell types.

The epithelial cell-specific integrin, CD103 (alpha E integrin), defines a novel subset of alloreactive CD8+ CTL.

The interaction of CD8+CTL with epithelial layers is an important but poorly defined aspect of organ allograft rejection. We herein report that CD103 (formerly alpha E integrin), a known receptor for the epithelial cell-specific ligand E-cadherin, is expressed by a major subset of CD8 + CTL elicited in response to allogeneic renal epithelial cells (REC). In contrast, CD103 was expressed poorly on CD8 + CTL generated in the conventional manner by stimulation with allogeneic leukocytes, although expression could be dramatically up-regulated by supplementing cultures with REC or exogenous TGF-beta 1. That TGF-beta controls the expression of CD103 on CD8+ CTL was further supported by the capacity of anti-TGF-beta mAb to block the generation of such cells in anti-REC cultures. Clonal analyses of anti-REC cultures revealed that individual CD8+ CTL clones were discretely CD103+ or CD103-, nd maintained their respective phenotypes independently of the cell type used for clonal restimulation. In a mouse model of graft-vs-host disease, 16.4 +/- 2.7% of CD8 cells that infiltrated host kidneys were CD103+ (n = 4). CD8 kidney-infiltrating lymphocytes were predominantly of donor origin and displayed an activated/memory phenotype (CD62L-, CD44high), consistent with expression of CD103 on a CD8 effector subset elicited in vivo following allogeneic transplantation. Taken together, the present data demonstrate that CD103 identifies a novel CD8 effector subset and, moreover, that such cells may comprise a significant component of the response to allogeneic tissues. The potential for CD103+ CTL as an important effector mechanism in organ allograft rejection, and more generally, as a mechanistic basis for tissue-specific immune phenomena, is discussed.

Dominance of tissue-restricted cytotoxic T lymphocytes in the response to allogeneic renal epithelial cell lines.

Our current knowledge of cytotoxic T lymphocytes (CTL) is largely derived from studies of effector populations generated in allogeneic mixed leukocyte cultures (MLC) and assayed for lytic activity to lymphoid cell (LC) targets. We herein report that the CTL response to allogeneic renal epithelial cell lines (REC) is dominated by effectors that efficiently lyse REC targets but show little cross-reactivity with LC targets. In contrast, CTL generated against allogeneic spleen cell stimulators (ie., in MLC) lysed REC and LC targets at comparable levels. Lytic activity in both types of cultures was mediated by CD8+TCRalpha/beta+ cells directed to classical H2 class I alloantigens. Anti-REC effectors cross-reacted with fibroblast and macrophage targets but not with targets commonly used to detect alloreactive CTL, such as lipopolysaccharide- or Con A-stimulated lymphoblasts or lymphoid tumor lines, whereas MLC-elicited effectors efficiently lysed all targets. CTL clones propagated from anti-REC cultures exhibited the same allospecificity and tissue specificity as bulk anti-REC effectors. Individual CTL clones were highly heterogeneous in their capacity to recognize the same class I alloantigen expressed on cells derived from different tissues. These data demonstrate that the cellular environment in which CD8 precursors encounter class I alloantigens can have a profound effect on the cell-type specificity of CTL populations. An important implication of these data is that conventional assays of CTL lytic activity may fail to reveal a significant component of the host response to allogeneic tissues.