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The Effect of Vitamin C Nutriture on Complement Component C1q Concentrations in Guinea Pig Plasma^1,2,3,

Graduate Division of Nutrition, University of Texas, Austin, TX 78712

This study shows that guinea pigs fed 100 times the amount of vitamin C needed for growth and for prevention of scurvy have elevated levels of complement component C1q. C1q is a plasma protein rich in hydroxyproline, an amino acid whose biosynthesis requires ascorbate. C1q is essential for host defense against pathogens, both as a component of the classical complement pathway and as an opsonin in the phagocytosis process. We measured C1q in vitamin C-depleted guinea pigs that had been repleted for 4 wks with the following daily doses of ascorbate (mg/100 g body wt): 0.50 (suboptimal), 2.0 (adequate), 10 (ample) and 50 (tissue saturating). We measured C1q in three ways: indirectly by quantifying protein-bound hydroxyproline and directly by hemolytic assay and by immunodiffusion against anti-C1q. Regardless of the method, plasma C1q was 30–50% higher in animals fed tissue-saturating ascorbate than in those fed adequate or suboptimal amounts of the vitamin (p < 0.05, one-way analysis of variance, least significant difference test). These data confirm and significantly extend earlier work that provided indirect evidence for a relationship between C1q and ascorbate nutriture in the guinea pig. They are consistent with a possible relationship between ascorbate nutriture and host defense.

KEY WORDS: • vitamin C • immunity • guinea pig • complement component C1q

¹ This research was based on the doctoral dissertation submitted to the University of Texas, Austin, TX, in July 1986.

² This work was supported in part by a Biomedical Research Support Grant, University of Texas, Austin, TX 78712.

³ A preliminary report of this work was presented at the Symposium on Nutritional Regulation of Immunity and Infection associated with the Sixth International Congress of Immunology, Toronto, Ontario, Canada, 3–5 July 1986.

⁴ Present address: Department of Family Resources and Human Development, Arizona State University, Tempe, AZ, 85287.

⁵ Department of Complement Research, Cytotech, Inc., San Diego, CA 92121.

⁶ To whom correspondence should be addressed.

Manuscript received 23 September 1986. Revision accepted 1 December 1986.

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