Neutralization of Bacteriophage by Normal Serum

Abstract

NORMAL mammalian serum of most species is capable of neutralizing bacteriophages of the Escherichia coli T series. This activity of normal serum has been attributed to the properdin system although a lack of correlation between properdin-levels and phage-neutralizing activity was noted with certain sera¹. Recent work by Cowan², moreover, in which several human sera were assayed for activity against T2, T6, and T7, indicated that the phage-neutralizing activity of a serum against one of the phage types was not correlated with its activity against the other two. These results suggested that the properdin system, essentially non-specific in its action, could not adequately account for the activity of normal serum against the three phage types. Cowan postulated, therefore, that properdin might be a family of cross-reacting antibodies capable of combining with zymosan. Similar considerations are applicable to other activities of normal serum. Our own findings in studies of the bactericidal action of normal serum against several species of Enterobacteriaceae indicated that bactericidal antibody of marked specificity plays the major part³.