Interferon-γ-based mixed lymphocyte culture as a selection tool for allogeneic bone marrow donors other than identical siblings

Selection procedures in bone marrow transplantation (BMT) would benefit from the development of easy-to-perform cellular assays with high discriminative power. We tested a cytokine-based mixed lymphocyte culture (MLC) and compared its outcome to the routinely used MLC, helper T-lymphocyte precursor (HTLp)-f and cytotoxic T-lymphocyte precursor (CTLp)-f assays. Interferon (IFN)γ was selected as a marker cytokine for (deleterious) T-helper 1 like responses and 36 (potential) BMT donor–recipient pairs were analysed. The IFNγ-MLC appeared sensitive to HLA class II (subtype) differences, but not to isolated class I differences, or to mismatches other than HLA (identical siblings). The test enabled a distinction between combinations with positive MLC (proliferation) and HTLp-f, exemplified by the fact that although high IFNγ levels were observed in the class II mismatched group, certain DRB3, DQB1-subtype and DRB1-subtype mismatches did not give rise to IFNγ production. This might be of relevance for the detection of so-called permissible mismatches. With regard to prediction of acute graft-versus-host disease (aGVHD) in unrelated BMT, the data indicated that high levels of IFNγ coincided with severe aGVHD, whereas low levels were largely associated with grades 0–I. However, in the case of isolated class I mismatches the test had no predictive value. The cell-saving IFNγ-MLC provides an alternative for the assays currently in use, but should be employed along with an assay that is sensitive to class I differences to correct for false negatives. Consequently, a combination of IFNγ-MLC and CTLp-f assays seems most promising for donor selection, other than identical siblings.