CGM1a antigen of neutrophils, a receptor of gonococcal opacity proteins

Neisseria gonorrhoeae (GC) or Escherichia coli expressing phase variable opacity (Opa) protein (Opa(+) GC or Opa(+) E. coli) adhere to human neutrophils and stimulate phagocytosis, whereas their counterparts not expressing Opa protein (Opa(-) GC or Opa(-) E. coli) do not, Opa(+) GC or E. coli do not adhere to human lymphocytes and promyelocytic cell lines such as HL-60 cells, The adherence of Opa(+) GC to the neutrophils can be enhanced dramatically if the neutrophils are preactivated, These data suggest that the components binding the Opa(+) bacteria might exist in the granules, CGM1a antigen, a transmembrane protein of the carcinoembryonic antigen family, is exclusively expressed in the granulocytic lineage, The predicted molecular weight of CGM1a is approximate to 30 kDa. We observed specific binding of OpaI(+) E. coli to a 30-kDa band of polymorphonuclear leukocytes lysates, To prove the hypothesis that the 30-kDa CGM1a antigen from neutrophils was the receptor of Opa(+) bacteria, we showed that a HeLa cell line expressing human CGM1a antigen (HeLa-CGM1a) bound Opa(+) E. coli and subsequently engulfed the bacteria, Monoclonal antibodies (COL-1) against CGM1 blocked the interaction between Opa(+) E. coli and HeLa-CGM1a. These results demonstrate that HeLa cells when expressing the CGM1a antigens bind and internalize OpaI(+) bacteria.