Neutrophils are critical in host defenses in the teleost Ictalurus punctatus, commonly known as the channel catfish. Neutrophils are one of the first cell types present in great numbers at sites of inflammation, attracted by chemotaxins, and transiently retained through the interaction of cell adhesion molecules. Channel catfish neutrophils adhere to a variety of extracellular matrix proteins, such as fibrinogen, fibronectin and gelatin, and the intensity of this response is dependent upon the activation status. In addition, the adhesion response of catfish neutrophils is calcium dependent. A high amino acid homology exist between the channel catfish and other mammalian CD18 molecules. Our experiments have demonstrated that channel catfish neutrophils have adhesive properties similar to those of mammals and that structurally similiar molecules, based on amino acid sequence homology, are present in the catfish.