Measurement of soluble mhc class i molecules in renal graft patients: A noninvasive allograft monitor

Abstract

We investigated the biochemistry of naturally occurring major histocompatibility complex (MHC) class I molecules in human serum and established a quantitative enzyme-linked immunoassay (ELISA) to determine soluble human leukocyte antigen (HLA) concentration. Peptides of 46, 40, 37, 35, and 12 kDa were isolated on affinity chromatography columns using two monoclonal antibodies (MoAbs), the anti-heavy chain W6/32 and the anti-β-microglobulin BBM. 1. These peptides were confirmed on Western blots by the HC-10 MoAb, which binds a monomorphic epitope on denatured heavy chains. In detergent-binding experiments, only the 46-kDa peptide could be isolated from solubilized cell membranes. No quantitative differences between serum and plasma HLAs of the same individual were measured. Soluble HLA expression in 12 renal graft recipients was measured over 1–3 mo posttransplantation. A highly significant increase of 50%–100% was noted during rejection episodes. Clinical signs of rejection were accompanied by poor renal function, including elevated creatinine values. After the crises had been managed, class I levels normalized to 0.3–1.5 μg/ml, which is the range in healthy persons. Patients who showed no rejection crises maintained constant levels within the period of study. We anticipate the application of soluble HLA measurement in clinical practice as a noninvasive graft monitor.