Tolerance to monovalent dextran of human mast cells.

In the present study it was investigated if monovalent dextran (Dx 1, HR 573, Promit) possibly involving activated complement is capable of inducing mediator (histamine) release from isolated human mast cells. Dx 1 in the absence or in the presence of 20% fresh human serum did not induce a histamine release from human mast cells. The "non-release" could be established statistically using a new sequential test which provides a substantial reduction of the average sample size required to reach a prescribed test power. In contrast, concanavalin A (Con A) or ionophore A 23187 caused a marked histamine release in the absence of human serum. In the presence of human serum the spontaneous histamine release was increased but the Con A- or ionophore-induced release was inhibited.