Titers of nine complement components, conglutinin and C3b-inactivator in adult and fetal bovine sera

Abstract

Titers of nine complement components, conglutinin and C3b-inactivator in bovine serum are presented. C1, C4, C5, C7 and C9 titers were very high in adult bovine serum and C2 and C8 were relatively low. Cl, C2 and C8 were quite heat-labile at 56°C, and C7 was moderately so, while C3 and C6 titers increased after heating. Prolonged storage at 0–4°C had little effect on the Cl, C5–9, conglutinin and C3b-inactivator activity of fetal bovine sera, but adversely affected C4. Fetal bovine serum contained approximately 1–3% of adult levels of conglutinin, Cl and C6, and 5–50% of adult levels of the remaining components except C3. C3 activity was undetectable in fetal bovine serum but present at the time of birth. A comparison of the complement component titers in ‘good’ and ‘bad’ lots of fetal bovine serum showed no relationship to their ability to support or inhibit in vitro immunoglobulin synthesis. Slight contamination of commercial bovine serum albumin and γ-globulin with complement components was observed.