Binding versus biological activity of Clostridium perfringens enterotoxin in Vero cells.

Cells resistant to $\text{Clostridium perfringens}$ enterotoxin were selected from cultures of highly sensitive Vero (African green monkey kidney) cells. Studies were done with the sensitive and resistant cells to determine the relationship between binding and biological activity. Binding studies using ¹²⁵I-enterotoxin revealed the apparent existence of high and low affinity binding sites for the enterotoxin on both cell types. The binding site density on resistant cells was found to be $\text{1}\text{10}$ that of sensitive cells. It was found that, even with high doses of enterotoxin, only partial affect upon DNA synthesis, membrane permeability, and plating efficiency was noted in resistant cells. It is concluded that without specific binding there is little or no ability of the enterotoxin to effect biological activity in cells.