The rapid identification of Chido and Rodgers antibodies using C4d-coated red blood cells.

A simple method for the recognition of anti-Ch and anti-Rg, using red blood cells coated in vitro with C4d, is described. Of 58 anti-Ch and 20 anti-Rg sera studied, all caused direct agglutination of C4d-coated red blood cells in tests incubated at room temperature. Moreover, selected sera were shown to react strongly (3+ to 4+) with C4d-coated red blood cells when tested by the indirect antiglobulin test without prior incubation at 37 C. Sera containing other high-titer, low avidity (HTLA) antibodies were either nonreactive with C4d-coated red blood cells, or reacted to the same degree with "non-C4d-coated" trypsin-treated red blood cells. Similar findings were obtained in tests with non-HTLA antibodies of assorted specificities, including a variety of alloantibodies to high-incidence red blood cell antigens. These findings indicate that the use of C4d-coated red blood cells in investigative immunohematology may aid in the rapid identification of Ch and Rg antibodies.