RESUMO
Neisseria gonorrhoeae (GC) or Escherichia coli HB101 (hereafter referred to as E. coli) expressing opacity (Opa) proteins adhere to human host cells and stimulate phagocytosis as a result of the interaction of certain Opa proteins to carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1; CD66a) receptors. Our experiments show that the Opa-CEACAM1 interaction does not play a significant role in adherence between these bacteria and dendritic cells (DCs). Instead, phagocytosis of GC and E. coli by DCs is mediated by the DC-specific intercellular adhesion molecule-grabbing nonintegrin, (SIGN; CD209) receptor. DC-SIGN recognition and subsequent phagocytosis of GC are limited, however, to a lipooligosaccharide (LOS) mutant (lgtB) of GC. This conclusion is supported by experiments demonstrating that HeLa cells expressing human DC-SIGN (HeLa-DC-SIGN) bind exclusively to and engulf an lgtB mutant of GC, and this interaction is blocked specifically by an anti-DC-SIGN antibody. The experiments suggest that LOS variation may have evolved as a mechanism for GC to avoid phagocytosis by DCs.
