Concanavalin A-dependent cell-mediated cytotoxicity in bronchoalveolar lavage fluid. Correlation with lung allograft rejection in mongrel dogs during cyclosporine dose tapering.

: Although cyclosporine (CsA) is widely used as the primary agent for inhibiting the rejection of organ allografts in man, the ideal immunosuppressive regimen for utilizing this drug is still uncertain. To investigate this question, a concanavalin A (con A)-dependent cell-mediated cytotoxicity (CDCMC) assay was used to examine the development of intragraft and peripheral blood cytolytic T lymphocyte activity during CsA dose tapering. These studies were conducted in a canine single-lung transplantation model that facilitates serial examination of intragraft effector cells by bronchoalveolar lavage (BAL). A remarkable correlation of increased intragraft CDCMC and clinical evidence of lung allograft rejection was observed during CsA dose tapering in some recipients. In other recipients CDCMC remained low and evidence of rejection was not observed during drug tapering. In contrast, peripheral blood CDCMC did not correlate well with evidence of rejection. Rejection phenomena observed after termination of CsA therapy were reversed by resumption of CsA treatment but were not reversed by administration of methylprednisolone. Furthermore, the increased level of CDCMC was diminished by reinstitution of CsA therapy at the initial dosage. Following termination of CsA therapy, a prolonged period of unresponsiveness was observed in nearly two-thirds of the recipients, and 60% of these latter dogs had unlimited survival of their lung allografts (median greater than 496 days). Intragraft CDCMC remained low during the periods of unresponsiveness and increased upon onset of rejection. We conclude that measurement of intragraft CDCMC is a useful in vitro method of monitoring lung allograft rejection, and therefore provides a technique for adjusting CsA dosage schedules to achieve maximally effective immunosuppression. The use of this assay for monitoring rejection of other organ grafts requires further investigation.