Cross-reactions between Haemophilus influenzae and nineteen other bacterial species.

Forty-one different antigens were demonstrated in an antigen preparation obtained by sonication of a Haemophilus influenzae (H. influenzae) type b strain, using crossed immunoelectrophoresis and antiserum obtained from rabbits. Antigens were characterized by absorption experiments with whole heat-killed bacteria, temperature resistance and protein and polysaccharide staining. Cross-reactions between H. influenzae type b and 19 other bacterial species were studied by various quantitative immunoelectrophoretic methods, using the reference system. A non-capsulated H. influenzae cross-reacted extensively (41 antigens) with H. influenzae type b and Haemophilus parainfluenzae, and Haemophilus haemolyticus showed considerable cross-reactivity with H. influenzae type b (26 and 32 antigens respectively), while antigens from eight other bacterial species cross-reacted to varying degrees with one to five H. influenzae antigens.