A cytotoxic factor for rat lymphocytes present in cobra venom is described and partially characterized. This cytotoxic factor (CF) was isolated by gel filtration on Sephadex G-100 from anticomplementary cobra venom factor (CVF) that had been previously partly purified by DEAE chromatography. The CF elutes from G-100 later than does the anticomplementary CVF. Estimates indicate a molecular weight of about 13,000. While rat lymphocytes are very sensitive to this factor as indicated by a decrease in capacity to exclude trypan blue, erythrocytes and peritoneal leukocytes are more resistant. The activity of CF is temperature dependent.

Studies of the local graft-vs-host reaction revealed an inhibitory influence of the partially purified DEAE-CVF that was attributable to the new CF of cobra venom. The role of the two CVF in GVH disease and other cellular immune functions is discussed.


This work was aided by grants from The National Foundation—March of Dimes, the American Heart Association and the United States Public Health Service (AI-10704, AI-00798).

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