Renal allograft-infiltrating lymphocytes. A prospective analysis of in vitro growth characteristics and clinical relevance.

One-hundred consecutive human renal allograft Tru-cut needle biopsies were studied for in vitro proliferation of T lymphocytes under restrictive culture conditions containing low-dose recombinant interleukin 2. Each biopsy was entered into a blinded code and evaluated prospectively for visual evidence of growth at 24 hr and for sustained growth. Those T cell populations exhibiting sustained growth were then evaluated for cell surface phenotype by FACS; for allospecific cytotoxicity by 51Cr release; for a proliferative response to alloantigen by incorporation of [3H]-thymidine; and for secretion of IL-2, IL-4, IFN-gamma, and TNF-alpha in response to alloantigenic stimulation by ELISA. All results were compared with clinical diagnosis, immunosuppression at time of biopsy, diagnosis and phenotype by immunopathology, short-term outcome and long-term graft survival. Growth at 24 hr was predictive of acute cellular rejection (P less than 0.0005), unrelated to chronic rejection (P = 0.663) or maintenance immunosuppression (P = 0.911), and inversely correlated with cyclosporine toxicity (P = 0.051) and treatment with OKT3 (P = 0.014). The CD4/CD8 ratio of the sustained T cell populations was unrelated to that seen on histological examination (correlation coefficient = -0.098 and 0.044 for diffuse and aggregate infiltrates, respectively). Cytotoxic specificity for HLA class II was mediated by CD4+ cells and for HLA class I by CD8+ cells. Enhanced secretion of IL-2 in response to alloantigen distinguished those cells associated with irreversible allograft damage from those associated with complete functional recovery (P = 0.01). This study demonstrates that early evaluation of T cell proliferation in vitro identifies activated T cell infiltrates mediating acute cellular allograft rejection in a time frame suitable for clinical diagnostic application. It strengthens the concept that donor-specific cytotoxicity is governed by the stabilization of the alloantigen-T-cell receptor interaction by the accessory molecules CD4 and CD8, but either interaction is equally able to participate in an episode of acute rejection. Irreversible graft injury is associated with infiltrating cells that are capable of amplifying their responsiveness through secretion of IL-2.

Duke Scholars

Author Allan Douglas Kirk Surgery, Abdominal Transplant Surgery

Author Ralph Randal Bollinger Surgery