Cobra venom as a lytic and anticomplementary substance has been known since 1900 (1). More recently, Nelson (2) separated a nontoxic component of cobra venom and showed that it was selective in its action in that only C3c was destroyed.Nelson also recognized that a serum cofactor was essential to the inactivation of the complement system by the purified cobra venom factor (CVF) 1 and Mfiller-Eberhard and his associates (3) defined a proinactivator, a 5S pseudoglobulin of a 3,-mobility in human serum essential to the inactivation of the complement system. Consonant with early work on the hemolytic action of cobra venom, Pickering et al. (4,5) showed that this purified cobra venom factor eluted from a single protein band on polyacrylamide gel can produce lysis of guinea pig red blood cells in the presence of fresh serum. This lyric activity was shown to be a function of the terminal components of the complement system and was found not to involve any of the complement components which act in the earlier steps of the complement cascade when the system is activated by antigen-antibody complex. Subsequently Ballow and Cochrane (6) have confirmed these findings and Shin et al. (7) have reported that acting through the proinactivator of the complement system, the cobra venom factor inactivates C5, 6, 7, 8, and 9 in vitro.These studies established that the cobra venom factor can utilize the entire terminal complement sequence and release chemotactic factors from C3 and C5 without engaging the earlier components. These observations are in keeping with studies by Gewurz et al. (8,9) and Mergenhagen et al. (10) which had indicated that the complement sequence can be activated by separate pathways which differ from the classical immunological mechanism of activation. In the present study we have applied the cobra venom factor pathway to study the complement system in the
Of eight lymphoblastoid cell lines studied five were insensitive to both the anticellular and antiviral activities of human leukocyte interferon, and two were sensitive to both activities. One line could not be fully evaluated since it was not possible to study its sensitivity to the antiviral activity.
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