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 (CD14bright) while approximately 15% of monocytes expressed this antigen at a lower level (CD14dim). Three times as many CD14dim monocytes expressed CD16 (Fc gamma RIII) as did CD14bright monocytes in both cord and adult preparations, while its level of expression (mean fluorescence intensity) was significantly reduced on cord CD14dim monocytes relative to adult CD14dim monocytes. The percentage of cord blood CD14dim monocytes expressing human leucocyte antigen-DR (major histocompatibility complex class II antigen) was significantly reduced relative to adult CD14dim cells; however, the level of expression of this antigen was greater on both cord and adult CD14dim monocytes compared with CD14bright cells. Cord CD14bright cells expressed CD36 (OKM5) to a greater extent than did their adult counterparts. The level of expression of CD62L was reduced on cord CD14dim cells compared with adult CD14dim cells. CD11b (CR3) was expressed both on a higher percentage of cells and also with a greater intensity on both cord and adult CD14bright monocytes compared with their CD14dim 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.