Serologic comparison of a monoclonal anti-C3d with commercial antiglobulin reagents

The serologic reactivity of a monoclonal anti-C3d and commercial "monospecific" anti-C3 and polyspecific antiglobulin reagents was compared. The testing consisted of a direct antiglobulin test performed on donor and patient cells and on in vivo and in vitro complement-coated cells; an indirect antiglobulin test was performed with low-ionic-strength solution crossmatches. The monoclonal anti-C3d demonstrated reactivity very similar to that of the commercial heterogeneous rabbit anti-C3d; it gave relatively few weak "false positive" reactions with normal donor and patient red blood cells, and comparably strong reactions with in vitro and in vivo C3d-coated red blood cells. The results suggest a promising future for monoclonal antiglobulin reagents.