Blood serum digested by trypsin yields split products which, when injected into the skin of normal rabbits, rapidly increase the permeability of small cutaneous vessels. This is likewise followed in the affected tissue by prompt local migration of polymorphonuclear leukocytes.
The tryptic digest of blood serum can be purified by methods previously described (3). The resulting crystalline substance alters the permeability of the capillary wall and favors local migration of leukocytes in a manner similar to leukotaxine proper. The present observations indicate that leukotaxine, or a substance having at least identical biological properties, appears to have been formed by proteolytic enzymatic action on an otherwise relatively inactive blood serum. This finding serves as additional evidence in support of the view that leukotaxine, recovered from inflammatory exudates, is probably an intermediary product of protein catabolism.