The mast cell-rupturing component present in the lysosomes of rabbit exudate PMN neutrophil leukocytes has been identified and some of its physical and chemical properties have been described.

The active agent is a low molecular weight (1200 to 2400) polypeptide containing a relatively large proportion of the basic amino acid, arginine. It is thermostable and dialyzable, and does not cause contraction of the isolated guinea pig ileum. The mast cell-rupturing activity of the agent is destroyed by trypsin.

A second permeability factor with a larger molecular weight is present in crude extracts of PMN granules. Although this substance does not lyse mast cells, it is capable of evoking delayed permeability responses in rabbit skin.

This content is only available as a PDF.