HLA typing and lymphocytotoxic crossmatches using conventional techniques or immunobeads. A comparative study.

In a prospectively designed comparative study, HLA class I and class II typing was performed after B/T lymphocyte separation by nylon wool (NIH technique) or using immunomagnetic beads (IMB technique). Samples from 70 healthy individuals (group A) and from 47 patients with potential typing problems (group B) were examined. Complete typing failures occurred more frequently with NIH than with IMB. Except for class I in group A, the rate of correct decisions for antigen assignment was significantly higher with IMB. For class II serum reactions, specificity, predictive value and efficiency were superior for IMB, while sensitivity appeared higher for NIH. This can possibly be explained by a prozone effect which was observed in 9 of 36 titration experiments only with the IMB technique. Correlation of both methods in 104 crossmatches prior to kidney transplantation was poor using peripheral blood lymphocytes, but excellent with spleen cells. In addition to the important advantages of the IMB technique for potential problem cases, especially for class II, typing time is reduced to one third, which is of particular clinical importance in kidney transplantation. However, lymphocytotoxic crossmatches prior to transplantation, if performed by IMB, should be carried out using different serum dilutions or with donor spleen cells instead of peripheral blood lymphocytes.