Positive flow cytometry crossmatch reactivity with pronase-treated T-cells induced by non-HLA auto-reactive antibodies in human immunodeficiency virus-infected patients

Historically, a positive flow cytometry crossmatch (FCXM) has been considered a contraindication for transplantation. Although interpreting the results of the T-cell FCXM has had few problems, the B-cell FCXM has been problematic due to the presence of Fc receptors on the cell membrane. IgG can bind to Fc receptors, resulting in increased background fluorescence, affecting the sensitivity and specificity. Pronase treatment of lymphocytes was subsequently introduced to improve the sensitivity and specificity of the B-cell FCXM. However, pronase treatment of both Tand B-cells in a single tube has been widely adopted for the 3-color FCXM. Although pronase treatment has been shown to increase the sensitivity and specificity of the B-cell FCXM, its effects on the T-cell FCXM have not been well documented. In this regard, we have observed a significantly high rate of positive T-cell FCXM results in the absence of anti-HLA donor-specific antibodies (DSA) in patients infected with the human immunodeficiency virus (HIV). This study was aimed at determining the cause of these aberrant results.