Inhibition of the Bactericidal Activity of the Properdin System by Zymosan and Other Properdin Binding Agents

[摘要] Sixteen preparations of cell walls and polysaccharides from Gram-positive and negative bacteria and from yeasts, all of known reactivity toward the properdin system as defined by the Zymosan assay, have been examined for ability to inhibit the bactericidal activity of serum. The indicator strain used ( Shigella dysenteriae ) was one previously shown to be sensitive to the properdin system.In competitive inhibition tests where bacteria and test preparation were added simultaneously to a bactericidal concentration of serum, the most active inhibitory agents were those that were known to inactivate complement in addition to combining with properdin. Preparations that combined with properdin but did not inactivate complement had 50- to 100-fold lower inhibitory activities. Certain anomalous results are explained on the basis of differences in reaction rates.Cell walls from a variety of Gram-positive and negative bacteria resembled Zymosan in their ability, when used as absorbing agents, to remove the bactericidal activity of human serum. Such absorbed serum is termed RPb.A study was also made of the effect, on RPb formation, of varying the temperature and time of absorption of serum with Zymosan. The effect of these variables accorded, in general, with the known characteristics of interaction of Zymosan with properdin and with the third component of complement.The results are discussed in relation to the general concept of properdin as a normal serum constituent differing from antibody in its broad spectrum of serologic reactivity and in having exacting requirements for its interactions, but resembling antibody in forming a bactericidal system with complement. The possible relationship of properdin to normal bactericidal antibodies is also briefly considered.

[学科分类] 生物科学（综合）