MACROPHAGE CANDIDACIDAL ACTIVITY IN HUMAN NEONATES: DECREASED SENSNIVITY TO MODULATION BY IFN-γ

Abstract

In an attempt to understand the mechanisms of host defense in the term neonate against candida, we studied interaction between Calbicans and monocyte-derived macrophages (MDM) cultured for 5 days from the cord blood. In the presence of 25% normal adult serum, the extent of phagocutosis of candida was equivalent with cord or adult MDM. In contrast to candida, MDM did not phagocytose non-opsonized group B Streptococcus type III, Mannosylated BSA (Man BSA, molar ratio of mannose to BSA = 23:1) inhibited non-opsonic ingestion of candida by cord and adult MDM 74 and 87 inhibition by 64 and 320 pg mannose/ml, respectively, after 60 min incubation means, n=6), suggesting a role for the mannose receptor. Cord MDM killed both opsonized and unopsonized Calbicans as effectively as did adult MDM (n=7) However, exposure of adult and cord MDM to IFN-γ (10-500 U/ml) gave quantitativel different results in candida killing and O release maximal increase in these functions with adult MDM were achueved with 100 U/ml IFN-γ, whereas no enhancement with cord MDM could be detected after treatment with 100 Uml, and at 500 Uml there was still a significantly lower killing and O. release by and MDM compared to adult cells. These data suggest that: 1. clearance of candida both the blood stream may occur in the absence of full opsonization a condition that might exist in the newborn; 2 resistance of cord MDM to the effect of IFN-γ may represent a developmental immaturity of human Phagocytes.