A comparison of the anaphylactoid actions of a synthetic linear dextran and a natural branched dextran.

Synthetic linear dextran of molecular weight 40,000 produces the systemic anaphylactoid reaction in rats although it is about 4 times less active than the natural branched dextran of similar molecular weight. Similarly, it is less active on local injection into the foot or skin. However, in rats which have been bred for non-reactivity to systemic dextran, it is more active on local injection, resembling the activity of a branched natural dextran of much lower molecular weight (6,000). In human skin, the synthetic linear 40,000 sample is also more active than the natural branched sample of similar molecular weight in producing a wheal and erythema. The results suggest that the dextran receptor in the skin of man may be similar to that in rats genetically resistant to systemic dextran.