Studies on lectins of amago (Oncorhyncusrhodurus) I. Amago ova lectin and its receptor on homologous macrophages

A lectin was found in the ova of amago, a Japanese trout ($\text{Oncorhyncus}$$\text{rhodurus}$), which agglutinates rabbit, rat and human B-type ery-throcytes. The hemagglutination was specifically inhibited by monosaccharides, L-rhamnose, D-galactose, and their C₂ and C₄ analogs, and p-nitrophenyl-α-D-galactoside and melibiose, indicating a binding specificity for α-L-ramnosyl or α-D-galactosyl type sugar moiety. To study its interaction with homologous cells, amago peritoneal macrophages were isolated from corn starch-stimulated peritoneal exudates. The lectin-rabbit erythrocyte complexes were found to adhere onto the macrophages harvested on the 4th day or later after the stimulation, but not to those obtained within 3 days; the latter macrophages acquired the complex-binding capacity when cultured for 3 to 4 days $\text{in}$$\text{vitro}$. These findings indicated that a lectin receptor is expressed on peritoneal macrophages after inflammatory stimulation. Similar lectin receptor-bearing macrophage-like-cells were also detected during $\text{in}$$\text{vitro}$ amago head kidney culture. This suggested that the inflammatory induced peritoneal macrophages may be differentiated from the head kidney macrophage precursor cells and during this process the ova lectin receptors also become expressed.