Differential expression of function-related antigens on newborn and adult monocyte subpopulations

Umbilical cord blood and adult peripheral blood monocytes were separated into two subpopulations, based on the intensity of CD14 expression, and the coexpression of various antigens associated with monocyte function was examined. The majority of cord and adult monocytes expressed CD14 at a high density (CD14(bright)) while approximately 15% of monocytes expressed this antigen at a lower level (CD14(dim)). Three times as many CD14(dim) monocytes expressed CD16 (Fc gamma RIII) as did CD14(bright) monocytes in both cord and adult preparations, while its level of expression (mean fluorescence intensity) was significantly reduced on cord CD14(dim) monocytes relative to adult CD14(dim) monocytes. The percentage of cord blood CD14(dim) monocytes expressing human leucocyte antigen-DR (major histocompatibility complex class II antigen) was significantly reduced relative to adult CD14(dim) cells; however, the level of expression of this antigen was greater on both cord and adult CD14(dim) monocytes compared with CD14(bright) cells. Cord CD14(bright) cells expressed CD36 (OKM5) to a greater extent than did their adult counterparts. The level of expression of CD62L was reduced on cord CD14(dim) cells compared with adult CD14(dim) cells. CD11b (CR3) was expressed both on a higher percentage of cells and also with a greater intensity on both cord and adult CD14(bright) monocytes compared with their CD14(dim) counterpart. These results show that significant differences exist between cord and adult monocyte subpopulations with regard to expression of various antigens associated with specific effector function.