Serum opsonins of control children of different ages.

Sera from a group of randomly selected control children between the ages of one and fourteen years were assessed for opsonic activity utilising the Neutrophil Iodination Micro-Method (NIMM). The opsonic capacity of fresh and heat inactivated serum from these children was compared with that of adult controls utilising the following micro-organisms: C. albicans, S. cerevisiae, zymosan, S. aureus (Oxford and Cowan I strains), S. epidermidis, E. coli meningitidis, and a nonpathogenic strain of E coli. The overall opsonic capacity of children under the age of four was similar to that of the adults and the older children (four to fourteen years) for all the micro-organisms tested except C. albicans. With five of the eight micro-organisms tested the heat stable opsonic activity of children in the younger age group was significantly lower than the other two groups tested. It is suggested that opsonic function in children approaches that of adults around the fourth year of life.