Tests for penicillin allergy in man. II. The immunological cross-reaction between penicillins and cephalosporins.

The immunological cross-reaction between penicillins and a cephalosporin derivative (cephaloridine CEPR) has been investigated. Cross-allergenicity was studied in twenty-four patients with established penicillin allergy using a variety of tests. Skin tests, quantitative leucocyte challenge (estimating histamine release by allergen) and lymphocyte stimulation (transformation) tests were performed, using CEPR, conjugates of CEPR with human serum albumin (HSA) and bovine gamma-globulin (BGG), benzylpenicillin and benzylpenicilloyl (BPO) conjugates with HSA and BGG. A cross-reaction was clearly established in the majority of patients. The highest percentage of positive results (cross-allergenicity) was obtained in the leucocyte challenge test (80 per cent with CEPR.BGG), followed by the lymphocyte stimulation test (50 per cent with CEPR.BGG), and then the skin test (46 per cent with CEPR.HSA). None of ten non-allergic controls gave a positive result in these tests. Three of the penicillin allergic patients had received cephaloridine, and all three developed allergic reactions. Cross-antigenicity has also been shown by haemagglutination and haemagglutination-inhibition tests on serum from larger groups of penicillin-allergic patients (including the previously mentioned twenty-four patients), and of non-allergic controls, who had anti-BPO antibodies.