Among the human extracellular pathogens known to bind to human CEACAM1, Neisseria gonorrhoeae and Neisseria meningitidis have been shown to bind via the expression of their Opa (colony opacity-associated) proteins leading to adherence and invasion into epithelial cells [11, 23] and engulfment by neutrophils [8, 23, 24] , as well as suppression of the T-lymphocyte response [25] and killing human B cells [26] effects that presumably inhibit antibody production. As mentioned above, the inhibitory activity is mediated by phosphorylation of the ITIMs on the long form of CEACAM1 and subsequent recruitment of SHP1/2 [13, 27] that can disrupt phosphorylation of important receptors, including the insulin receptor [28] , EGFR [29] , TCR [14, 15] , BCR [17] , and TLR2 [30] . In the case of Neisseria gonorrhoeae, neutrophils, due to their high levels of CEACAM1 expression, are a major target for spreading the infection in the urogenital tract. A major limitation to studying these interactions in vivo has been the lack of an animal model, since murine CEACAM1 is not a receptor for these human pathogens. In order to overcome this limitation, we have generated a human CEACAM1 transgenic mouse that faithfully expresses human CEACAM1 in the expected tissues, including neutrophils. We demonstrate here that the neutrophils from the transgenic mice as well as human neutrophils bind gonococcal Opa 52 protein expressed on E. coli. Thus, these mice should serve as an appropriate animal model at least for studying some aspects of the human pathogenesis of Neisseria gonorrhoeae infections.