A possible link between the ability of rat isolated peritoneal mast cells to release histamine when challenged with dextran and the proteins in their plasma membranes.

The plasma membranes of peritoneal mast cells from rats specifically bred for resistance to the dextran anaphylactoid reaction contain a polypeptide of molecular weight about 74,000 daltons which is deficient in those from rats which show the reaction. It is suggested that this polypeptide modifies the dextran receptor in the resistant rats so that histamine release cannot be induced when their mast cells are challenged with dextran.