Treatment of serum with the insoluble polysaccharide residue of yeast cells (zymosan) has been shown (a) to decrease the bactericidal power of serum for certain bacteria; (b) to remove from some sera a factor essential to the interaction of zymosan with the third component of complement. The adsorbed protein (properdin) was eluted from zymosan and found to contain α2, β and some γ globulins. It was shown to restore partially the normal characteristics to treated serum (RP).
Properdin levels have been estimated in the sera of eighteen burned patients and in twelve normal subjects. There was evidence of a reduced level in the patients' sera. The limitations of the assay method are discussed.
Bactericidal activity of normal serum containing properdin was tested against nineteen Gram-negative bacilli isolated from burns. Ps. pyocyanea, Proteus and Klebsiella, which are commonly found in burns, were with one exception resistant or slightly sensitive to the bactericidal action of this serum. Bact. coli, which is uncommon in burns, was usually highly sensitive.
From our preliminary studies reported here it would seem that the properdin system cannot be expected to kill the flora in established infections of burns, and properdin is therefore unlikely to prove useful as a therapeutic agent. However, it probably has an important role as one of the defence mechanisms of uninfected tissues.
We wish to thank Dr Derrick Rowley and Dr A. C. Wardlaw for helpful discussions, and Dr W. Weiner for his advice and co-operation. We are grateful to Miss Stella Baar, F.R.I.C., for N and P analyses.