ENDOCYTOSIS AND INTRACELLULAR DEGRADATION OF HETEROLOGOUS PROTEIN BY EOSINOPHILIC GRANULOCYTES ISOLATED FROM RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) POSTERIOR INTESTINE

Adherence capacity to tissue substrate, endocytosis capacity for heter ologous and homologous proteins, and proteolytic activity were determi ned in intestinal granulocytes (EGCs) isolated from healthy adult rain bow trout. The percentage of cells that could adhere to a smooth plast ic surface increased with increasing incubation time. Endocytosis was effective for heterologous (human immunoglobulin G, IgGh; ovine somato tropin, oST) but not homologous proteins (recombinant trout somatotrop in, rtST). The activity of cathepsin D increased significantly after t he endocytosis of a heterologous protein. Finally, the analysis of imm unoblots of homogenates of granulocytes incubated in the presence of t he two different proteins was used to show the endocytosis and degrada tion of heterologous proteins. These results show that isolated EGCs c an endocytose and degrade heterologous proteins.