Human leucocyte antigen-defined microchimerism early post-transplant does not predict for stable lung allograft function.

Microchimerism is the presence of foreign cells in an individual below 1% of total cells, which can occur in the setting of solid organ transplantation. This study quantitated donor-derived cellular subsets longitudinally in human leucocyte antigen (HLA)-mismatched lung transplant recipients (LTR) during the first post-operative year and evaluated the pattern of peripheral microchimerism with clinical outcomes. Peripheral blood mononuclear cells (PBMC) isolated from non-HLA-B44 LTR who received HLA-B44 allografts were sorted flow cytometrically into three cellular subsets. Real-time quantitative polymerase chain reaction (qPCR) demonstrated that donor-derived HLA-B44 microchimerism is a common phenomenon, observed in 61% of patients. The level of donor-derived cells varied across time and between LTR with frequencies of 38% in the B cells/monocytes subset, 56% in the T/NK cells subset and 11% in the dendritic cells (DC) subset. Observations highlighted that microchimerism was not necessarily associated with favourable clinical outcomes in the first year post-lung transplantation.