Correlations between serum lipids and complement components in adults without demonstrated atherosclerotic disease

The variability due to age and sex and the reciprocal relations of serum IgG, IgA, IgM, C3, C4, total cholesterol (TC), HDL-cholesterol (HDL-C) and triglycerides (TG) were studied in 87 subjects (46 men and 41 women, aged 20-75 years) selected for the absence of significant atherosclerotic lesions. Serum IgA and C3 were higher in men than in women (P less than 0.05) mainly in the age group 41-60, while IgM and HDL-C were higher in women than in men (P less than 0.05 and P less than 0.01, respectively), especially in the age group 20-40. Direct univariate correlations with age were found for serum TC (P less than 0.0001), IgA (P less than 0.001), and C4 (P less than 0.01) but the latter correlations was confirmed only in women by multivariate analysis. These 3 variables had the major increment in the age group 41-60 in men, while in women the increase associated with age was more progressive or late. Univariate analysis showed a 'ring' of highly significant correlations (P less than 0.0001) involving serum lipids and complement components (TC-C4-C3-TG-TC). The correlation between TC and C4 was present only in men in multivariate analysis and improved with increasing age. These findings might represent a clue to explain the previously reported association between serum C4 and atherosclerosis.