C017-1A is a tumor associated antigen on colorectal carcinoma cells. A mouse monoclonal antibody of subclass IgG2A (MAb 17-1A) has been previously produced against the antigen for therapy. In a phase II study in patients with metastasizing colorectal carcinomas, leukapheresis was performed and isolated cells armed in vitro with MAb 17-1A. The mixture of MAb 17-1A and cells were infused into the patients. The aim of this procedure was to increase the number of cytotixic cells in the tumor lesion. Two cell purification techniques (A and B) using an IBM 2991 Blood Cell Processor are described. Procedure B gave the highest yield of mononuclear cells (7.52x109 vs 5.17x109, p<0.01) as well as significantly higher total numbers of monocytes and NK cells. The relative ADCC activity of the two cell isolates were similar A positive correlation between the frequency of Leu-M5+ cells (monocytes) and 51Cr release was observed. Increasing amounts of 0KM1+ (CD11) cells suppressed ADCC. 35-40% of the cells bound MAb 17-1A after 1h incubation at room temperature. There was no substantial increase in cells binding MAb 17-1A upon further incubation. A strong positive correlation between the numbers of monocytes and cells binding MAb 17-1A was seen but also B lymphocytes, T lymphocytes and NK cells bound MAb 17-1A. More than 97% of the added MAb was unbound.
