[Age-dependence of the complement (beta 1A/C) serum concentration in healthy children (author's transl)].

In 496 sera of healthy children(cord blood, newborn infants, children up to 10 years of age) complement (C'3) was determined quantitatively by single radial immunodiffusion technique. Higher values are found in cord blood as compared to newborns during the first days of life. Adult levels are reached in infants aged 12 to 36 months. Complement is produced in excess. Normal concentrations do not necessarily exclude a pathologic situation. Abnormally high or low levels of complement (C'3) in the serum may point at pathologic processes. However, single determinations are of pathognomonic value only when low concentrations are found. Age dependency of C'3-levels in children has to be kept in mind when used for diagnosis.