Major granulocyte receptor mediating recognition and efficient opsonin-independent phagocytosis of CEACAM-binding microorganisms, including Neissiria, Moxarella and Haemophilus species, thus playing an important role in the clearance of pathogens by the innate immune system. Responsible for RAC1 stimulation in the course of pathogen phagocytosis. Interacts with S100A9/calprotectin. This interaction is calcium-dependent, but independent of CEACAM3 phosphorylation. CGM1a, the predominant CGM1 transcript, is granulocyte-specific. Not detected out of the granulocytic lineage, such as monocytes, lymphocytes, spleen, testis, colon, brain, liver, pancreas, thymus, ovary, placenta, skeletal muscle, prostate, small intestine, heart, lung and kidney. The cytosolic domain is involved in S100A9 interaction. Tyrosine-phosphorylated in response to microbial binding. Tyr-230 and Tyr-241 are both required for phosphorylation to be detected. Belongs to the immunoglobulin superfamily. CEA family. This is not the ortholog of rat CEACAM3.