A Novel Approach to Detect Donor/Recipent Immune Responses Between HLA-Identical Pairs

Abstract Renal transplant rejection and graft versus host reactions between HLA genetically-identical sibling (HLA gi ) donor/recipient (D/R) pairs are thought to result from minor histocompatibility antigen (mHAg) disparities. We have compared two methods of measuring HLA gi D/R T lymphocyte responses to “matured” dendritic cells: 1.) a modified Cylex assay of CD4+ ATP levels (MLDC-ATP) versus 2.)3 H-thymidine uptake (MLDC-3 H). The MLDC-ATP kinetics peaked at 48 hours versus the MLDC-3 H at 7 days, and appeared more sensitive. We tested HLA gi (normal) volunteer siblings (NLs), and D/R sibling pairs before and after renal transplantation (pre-Tx and post-Tx). The overall frequencies of positive responses in the MLDC-ATP for HLA gi NLs, pre-Tx, and post-Tx D/R pairs were 63%, 50%, and 42%, respectively. The percentage with reciprocal responses was 37.5%, 20%, and 22.22%, respectively. In one set of three HLA gi (NLs) siblings (two males and one female), there was a nongender-associated differential response. There was no MLDC correlation with class I MHC-associated mHAg (SSP) incompatibility, nor could some MLDC positive reactive pairs theoretically process the necessary HLA-class I restriction molecules for presentation of known (nanomeric) mHAg peptides. Speculatively, the MLDC reflects class II MHC-restricted mHAg reactions (not yet definable), with possible effects of other polymorphic (nonhistocompatibility) immune response genes, and thereby may be a useful measurement of CD4+ T-cell HLA gi transplantation immunity.