Flow Cytometric AHG-CDC for HLA Crossmatch: A Pilot Study

Won, Dong Il

Abstract

BACKGROUND
For HLA crossmatch in organ transplantation, complement-dependent cytotoxicity (CDC) is a very useful methodology to detect donor-specific HLA antibodies and their complement fixing ability. In this preliminary pilot study, we investigated whether dead cells induced in anti-human globulin (AHG)-augmented CDC (AHG-CDC) reaction could be measured by flow cytometry ('FC AHG-CDC').
METHODS
This FC AHG-CDC measured the percentage of dead cells (% dead cells) after 7-aminoactinomycin D staining using 3 color flow cytometry. A total 45 flow cytometry crossmatch (FCXM) cases of 12 positives and 33 negatives were further tested using this FC AHG-CDC.
RESULTS
The % dead cells of FC AHG-CDC was significantly correlated with the mean fluorescent intensity ratio of FCXM (T cells: r=0.613, P=7.45x10(-6); B cells: r=0.404, P=0.006). The positivity rate of FC AHG-CDC among FCXM positive cases was relatively high: 80% (8/10) for T cells and 75% (9/12) for B cells. The negativity rate of FC AHG-CDC among FCXM negative cases was 100% (35/35) for T cells and 91% (30/33) for B cells.
CONCLUSION
In this pilot study, FC AHG-CDC could yield quantitative values, % dead cells, which was proportional to the level of complement-fixing cytotoxic antibodies against T and B cells, respectively, even without physical separation of cells or serial dilution of serum.