Carbohydrate and lectin interactions with Edwardsiella ictaluri and channel catfish, Ictalurus punctatus (Rafinesque), anterior kidney leucocytes and hepatocytes

Abstract. Seven isolates of Edwardsiella ictaluri were evaluated for channel catfish red blood cell and neutrophil agglutination properties and reactivity with lectins and carbohydrates. All isolates were agglutinated by lectin derived from Ricinus communis and the intensity of the agglutination reaction could be lessened or abrogated by premixing the lectin derived from Ricinus communis with β-D-galactose or α-L-fructose. Edwardsiella ictaluri isolates also sedimented much more rapidly when mixed with lectin derived from Ricinus communis than when mixed with other lectins. Premixing Ricinus communis with β-D-galactose had the greatest effect on slowing the rate of sedimentation. Two out of the seven E. ictaluri isolates were capable of agglutinating channel catfish red blood cells and anterior kidney neutrophils, and this agglutination could be prevented by the addition of β-D-mannose. Likewise, the per cent phagocytosis of E. ictaluri isolate 1389 (the most intense neutrophil agglutinator) could be dramatically reduced by the inclusion of mannose in the assay mixture. Anterior kidney leucocytes and hepatocytes primarily reacted with lectins derived from Canavalia ensiformis, Ricinus communis and Triticum vulgaris. The presence on channel catfish cells of carbohydrate-lectin receptors similar in function to those found on mammalian cells and the reaction of E. ictaluri with specific lectins suggest that bacterial clearance and lectinophagocyotosis may occur in a similar manner in catfish to that in mammals.