Penicillin and cephalosporin immunogenicity in man.

Whether cross-allergenicity exists between the penicillin and cephalosporin antibiotics is controversial. A solid-phase radioimmunoassay was adapted to detect drug-specific IgG, IgM and IgE antibodies. Penicillin and cephalothin-specific serum immunoglobulins were determined in patients' serum before and after a therapeutic course of sodium cephalothin. Changes in IgG, IgM and IgE antipenicillin and anticephalothin antibodies, respectively, occurred and were closely correlated to one another (r = 0.80--0.99, p less than 0.0005), indicating that antibody responses to penicillin and cephalothin were linked. This in vitro assay system should prove useful for further study of clinical drug allergies.