Correlation between serum lipid profiles and the ratio and count of the CD16+ monocyte subset in peripheral blood of apparently healthy adults.

BACKGROUND AND PURPOSE

Deposited vascular oxidized low-density lipoproteins (LDLs) are important triggers of the transformation of circulatory monocytes into macrophages. CD16+ monocytes have been reported to be the precursors of tissue macrophages. In this study, we sought to determine the relationship between serum LDL-cholesterol and the percentage and count of the CD16+ monocyte subset in the peripheral blood of healthy adults.

METHODS

We studied the correlations between serum lipid profiles and both peripheral CD16+ and CD36+ monocyte subset ratios and counts in apparently healthy adults (50 men and 50 women). Monocyte surface antigens CD16 and CD36 on CD14+ monocytes were detected using fluorescent triple staining and flow-cytometry. Surface staining was performed by incubating 1 x 10(6) blood mononuclear cells with phycocrythrin-conjugated anti-CD14, fluorescein isothiocyanate-conjugated anti-CD36, and respective control isotopes (mouse IgGs). A total of 5,000 cells were counted and the frequency of surface antigens was determined by FACscan.

RESULTS

A significant positive link between LDL-cholesterol and the CD16+ subset ratio was found by linear correlation analysis (p < 0.05) but not by multivariate regression analysis. Both linear correlation analysis and ANOVA revealed a significant inverse link between high-density lipoprotein (HDL)-cholesterol and the CD16+ subset ratio (both p < 0.01). By multivariate regression analysis, gender was the main significant determinant for the CD16+ subset ratio. When serum total cholesterol (TC) was excluded from the analysis to avoid the interference from collinearity between serum TC and LDL (r = 0.84), HDL-cholesterol became independently and inversely linked to the CD16+ subset ratio. There were independent inverse links between HDL-cholesterol and the counts of all monocytes, CD16+ monocytes, and CD36+ monocytes.

CONCLUSIONS

Our results suggest that circulating HDL-cholesterol may be much more important than LDL-cholesterol in affecting the transformation of circulatory monocytes into macrophages. The inverse link between HDL-cholesterol and the number of macrophage precursors in peripheral blood might contribute partly to the well-known antiatherogenic effect of HDL-cholesterol.