Ontogenic changes in serum immunoglobulins and C3 in vitamin-D deficient and malnourished rats

In both protein energy malnutrition and vitamin D deficiency, defects in some immunological functions have been noted, but the effects on complement and immunoglobulin concentrations have not been evaluated. We assessed the effects of malnutrition and vitamin D deficiency on immunoglobulins and C3 in rats in early postnatal life during weaning and early adulthood using the rocket immunoelectrophoresis technique. In well-nourished rats, the serum levels of IgG increased from 88.5 +/- 10.2 mg/dl in the newborn period to 883.4 +/- 104.8 mg/dl at weaning (day 19). The adult levels, 1,325.9 +/- 60.8 mg/dl, were attained by 35 days of age. Serum IgA was not detectable by our method until 20 days of age (1.1 +/- 0.2 mg/dl) and reached adult levels (13.4 +/- 3.2 mg/dl) by day 35. IgM was detectable in the serum of pups at 5 days of age (0.4 +/- 0.07 mg/dl), increased to 27.5 +/- 6.9 mg/dl at weaning and approached adult levels (93.7 +/- 9.9 mg/dl) at day 35. C3 levels at birth were only 36% of adult levels and did not change during the suckling period. They then increased to levels comparable to those of adults at the age of 35 days. Serum immunoglobulins and C3 in malnourished rats were not significantly different from age-matched control pups. In pups born to dams fed a vitamin-D-deficient diet from 3 weeks of age, only the serum IgG and C3 levels were significantly lower than those of normal pups at day 1 (IgG level: 65.2 +/- 6.1 vs. 88.5 +/- 10.2 mg/dl; C3 level: 20.3 +/- 6.9 vs. 36.2 +/- 3.1% of an adult level; p less than 0.005). Thus the increased susceptibility of malnourished young animals to infection does not appear to be related to a lowering of serum immunoglobulin and complement concentrations.