Characterization of an HLA-A3 restricted human kidney specific T cell clone.

BACKGROUND: The tissue specificity of a cytolytic T lymphocyte is determined by the MHC class I bound peptide it recognizes. We have developed an allorestricted human CTL clone, DBS 1.5, that recognizes an epitope found on HLA-A3+ kidney epithelial cells but not on HLA identical B-lymphoblastoid cells. The peptide recognized by this clone has been isolated from HPLC separated, acid eluted peptides from purified HLA class I molecules from HLA-A3+ kidney tissue. This peptide shares no sequence homology with any known protein. METHODS: To confirm the tissue specificity of the HLA-A3 restricted clone and the peptide it recognizes we have transfected the gene for HLA-A3 into a number of tumor cell lines both human and murine not expressing this antigen. The resulting transfected lines, confirmed by immunofluorescent staining, were used as targets to determine if expression of HLA-A3 alone was sufficient to allow recognition and lysis by the HLA-A3 restricted T cell clone. RESULTS: The HLA-A3 restricted T cell clone recognized HLA-A3 when expressed on human kidney epithelial cells and to a lesser extent on human lung epithelium and human epidermal cells. Of the tumor lines transfected with HLA-A3 only the human kidney tumor cell line was lysed at a level equal to the original kidney epithelial cell used to develop the clone. CONCLUSION: These results confirm that this allorestricted human CTL clone is tissue specific recognizing a peptide found in human epithelial tissue that must be presented in the context of HLA-A3 for recognition.

Indirect allorecognition of HLA class I peptides by CD4+ cytolytic T lymphocytes.

T-cell responses to alloantigens can occur either by "direct" recognition of donor MHC molecules, or "indirect" recognition of MHC peptides in association with self-MHC. To evaluate human T cells mediating indirect allorecognition, a CD4+ TCL and clones specific for HLA-A1 or HLA-B8 (residues 60-84) were generated from normal PBLs (A2,29 B62,- DR1,4 DQ3). Most clones were A1 specific (16 out of 17 tested), HLA-DR4 restricted (8 out of 8), and lysed targets pulsed with A1 peptide (16 out of 16). An amino acid substitution at position 86 of the DR4 beta chain (G -> V) abrogated the capacity of CD4+ CTLs to lyse target cells. Chloroquine treatment of A1-pulsed targets reduced their susceptibility to lysis, indicating a requirement for peptide processing. The TCL and clones were stimulated to proliferate by cells bearing intact HLA-A1 when autologous APCs were present, indicating that the epitope contained within the A1 60-84 peptide being recognized is produced when APCs process native HLA-A1. Furthermore, the clones and TCL did not recognize HLA-A1 on target cells carrying this allele plus self-HLA-DR4. These studies suggest a much wider role for CD4+ T cells in allograft immunity.

Cytolytic T lymphocytes from human renal allograft biopsies are tissue specific.

The cytolytic activity of T lymphocytes infiltrating renal allografts from recipients undergoing episodes of acute cellular rejection was studied. These T-cell populations, composed of both CD4+ and CD8+ cells, demonstrated significant cytolytic activity against both donor-derived KCLs and B-LCLs. In five of 21 biopsy-derived lines greater cytolytic activity was measured against donor KCLs compared to donor B-LCLs, suggesting the presence of kidney antigen-specific, MHC-restricted clones. Clones developed by stimulation with donor B-LCLs lysed both donor B-LCLs and KCLs while clones developed on donor KCLs as stimulator cells showed tissue specificity. Three of 26 clones recognized tissue-specific antigens in the context of donor MHC class I antigens lysing donor KCLs but not B-LCLs. These data demonstrate that a subpopulation of T cells recognizing kidney-specific antigens are present in biopsies of renal allograft recipients undergoing acute cellular rejection. This subpopulation of tissue-specific cytotoxic T lymphocytes may prove to contribute significantly to the pathology of allograft rejection.

Renal allograft infiltrating lymphocytes: frequency of tissue specific lymphocytes.

Acute rejection, mediated by T lymphocytes recognizing donor MHC class I and II, is a major factor influencing renal transplant survival. To define the specificity of these effector cells we examined cytolytic activity of graft infiltrating T lymphocytes (GIL) from renal biopsies of individuals undergoing acute cellular rejection. The majority of these cells recognized MHC class I on both donor kidney epithelial cells (KCL) and B-lymphoblastoid cells (LCL) suggesting these T cells recognized peptides from various tissues. However, cold target inhibition experiments demonstrated a significant proportion of GIL T cells were tissue specific. We reported previously that kidney specific CTL can be isolated from biopsies of kidney allografts undergoing acute cellular rejection. Here we extend that observation showing we were able to isolate tissue specific CTL from two additional biopsies. Greater than 10% of the clones isolated (4 of 36 and 5 of 37) from these biopsies were CTL recognizing donor KCL but not LCL targets suggesting that peptides, recognized in the context of donor MHC, were tissue specific. Repeated isolation of significant numbers of tissue specific CTL suggests these T cells play a role in allograft rejection and may be important effector cells mediating rejection in HLA matched transplants.