Detection of alloantibodies against non‐HLA antigens in kidney transplantation by flow cytometry

The presence of alloantibodies against human leucocyte antigen (HLA)-I and HLA-II antigens has been associated with hyperacute and accelerated graft rejections. However, occasionally these rejections occur in patients without donor-specific anti-HLA antibodies, suggesting the presence of other antigenic complexes that are shared by the graft and other cell populations. Usually, these antibodies are not routinely studied and their role in graft rejection is poorly understood. For this reason, we tested, by flow cytometry, the presence of panel-reactive alloantibodies (PRA) using different cell populations in 30 pre-transplant sera of kidney graft recipients. The patients studied had or had not hyperacute and accelerated rejection episodes (HARE) and did not have alloantibodies against HLA of their specific donors. We found that IgG and IgM alloantibodies directed against HLA-I antigens, different to the HLA-I antigens of the specific donors, as well as IgG against endothelium/monocyte antigens, IgM against platelets, and IgM against T cells are significantly associated with HARE, independently of the percentage of PRA. Our findings suggest that the detection of antibodies by flow cytometry against non-major histocompatibilty complex antigens may be useful as a pre-transplant crossmatch in living related donor kidney transplants to diminish the incidence of HARE.