The effects of leukocyte depletion on corneal neovascularization

The role of leukocytic infiltration in the initiation and maintenance of corneal neovascularization was studied in rats. Vascular ingrowth was induced by central cauterization of the cornea with silver nitrate and assessed after intraarterial perfusion of colloidal carbon. In normal rats, the mean vascular length was 0.33 mm. at 3 days and 0.63 mm. at 4 days. Whole-body x-irradiation with 800 rads depressed peripheral blood leukocyte counts to 1% of normal, prevented infiltration of monocytes, and reduced infiltration of neutrophils, but did not alter the neovascular response at 4 days. Combined treatment with radiation (800 rads) and repeated injections of antineutrophil serum (ANS) reduced peripheral leukocyte counts to nearly zero and eliminated infiltration of both monocytes and neutrophils. Despite the absence of leukocytes, neovascularization occurred in all corneas. However, the mean vascular length was reduced to 67% of control at 3 days and to 33% at 4 days. The results indicate that vascular growth can be initiated in the absence of leukocytic infiltration. The reduced neovascularization in totally leukopenic animals might be due to either the ability of neutrophils to facilitate or augment vascular growth or the nonspecific effects of treatment with radiation and antineutrophil serum.