MEMBRANE ANTIGEN AND LIGAND-RECEPTOR EXPRESSION ON NEONATAL MONOCYTES

The monocyte/macrophage cell lineage is an essential component of host defense. Functional deficiencies have been described in neonatal mono cytes, but knowledge of membrane antigen and receptor ligand expressio n in neonatal monocytes is incomplete. In this study, antigen and rece ptor ligand expression of cord blood monocytes (CBM) was examined and compared to adult peripheral blood monocytes (PBM). Leu-M3 and Leu-M5 antigens were shown to be present on all CBM. Using dual fluorescence microfluorometry, the percentage and intensity of expression of HLA-DR , CD4 antigens, Fc gamma and IL-2 receptors (IL-2R) on Leu-M3(+) and L eu-M5(+) CBM were compared to PBM. A lower percentage of expression of HLA-DR(+) (87 +/- 3% vs, 95 +/- 1%, p = 0.02) and FC gamma RII(+) (96 +/- 1% vs. 99 +/- 0.2%, p = 0.04) was noted on CBM. CD4, FC gamma RI, and FC gamma RIII expression on CBM were comparable to PBM. LPS stimu lation of CBM induced IL-2R expression and enhanced HLA-DR antigen exp ression as seen previously on PBM. These findings indicate that CBM ar e phenotypically comparable to adult PBM with deficiencies localized o nly to a few specific areas.