The flow cytometric detection of alloantibodies in screening for renal transplantation

Flow cytometric screening of sera using pooled chronic lymphocytic leukaemia (CLL) cells has previously been reported as a quick method for detecting HLA antibodies of the IgG class. In this study we investigated the sensitivity of this method in the detection of IgG and IgM alloantibodies, and its performance in serum screening when compared to conventional microlymphocytotoxic screening. Results indicate that flow cytometric screening is more sensitive in the measurement of IgG alloantibodies by up to five doubling dilutions, whereas the converse is true for IgM. IgM autoantibodies were found not to be detectable by flow cytometry. By testing a large number of sera by both methods in parallel, we have found that a significant proportion of sera exhibiting no activity or IgM activity alone on cytotoxic screening contain IgG antibodies detectable with a pool of CLL cells on the flow cytometer.