DISTRIBUTION OF COMPLEMENT REGULATORY PROTEINS, DECAY-ACCELERATING FACTOR, CD59 HOMOLOGOUS RESTRICTION FACTOR-20 AND MEMBRANE COFACTOR PROTEIN IN HUMAN COLORECTAL ADENOMA AND CANCER/

To clarify the events related to complement-mediated immune responses in human colorectal cancers, we immunohistochemically examined the dis tribution of decay-accelerating factor (DAF), CD59/homologous restrict ion factor 20 (HRF20), membrane cofactor protein (MCP) and terminal co mplement complex (TCC) in human colorectal adenomas and cancers, and t hen compared the findings with their distribution in normal colonic mu cosa. In the normal mucosa, TCC was not present on epithelial cells. W hereas DAF and CD59/HRF20 were present only occasionally on the apical surfaces of normal epithelial cells, MCP was diffusely distributed on the basolateral surfaces of most epithelial cells of the colon. These findings suggest that MCP has a primary role in the regulation of com plement activation on these cells. In adenoma cells, the expression of both DAF and CD59/HRF20 was enhanced. In cancer cells, the expression of CD59/HRF20 and MCP was diminished, whereas DAF expression was mark edly enhanced. Since DAF was frequently stained in the lumen of the ca ncer glands, it was suggested that DAF was released into the colonic l umen in patients with colorectal cancer.