Infection with Neisseria gonorrhoeae can trigger an intense inflammatory response, yet there is little specific immune response or development of immune memory. In addition, gonorrhea typically correlates with a transient reduction in T lymphocyte counts in blood, and these populations recover when gonococcal infection is resolved. Such observations suggest that the gonococci have a suppressive effect on the host immune response. We report here that N. gonorrhoeae Opa proteins were able to bind CEACAM1 expressed by primary CD4⁺ T lymphocytes and suppress their activation and proliferation. CEACAM1 bound by gonococcal Opa₅₂ associated with the tyrosine phosphatases SHP-1 and SHP-2, which implicates the receptor's ITIM (immunoreceptor tyrosine-based inhibitory motif) in this effect.