Alcohol use during pregnancy continues to be a significant issue but its contribution to adverse outcomes in the premature newborn remains understudied. We previously reported that approximately one in three very low birthweight (VLBW) premature newborns were exposed to alcohol in utero per maternal report. This exposure was linked to an increased odds of late onset sepsis (LOS) and bronchopulmonary dysplasia (BPD). In our animal models of in utero alcohol (ETOH) exposure, alveolar macrophage (AM) immune responses against bacteria were decreased in multiple species of newborn pups. These alterations included increased oxidant stress and delayed AM maturation but were improved by treatment with the antioxidant glutathione (GSH). In the newborn lung, the ontogeny of the mature AM remains controversial but fetal monocytes mature to AM via PU.1 in response to Granulocyte/Macrophage Colony Stimulating Factor (GM-CSF). In utero alcohol exposure decreases GM-CSF but its effects on circulating monocytes and different monocytic cell pools within the developing lung are unknown. For the adaptive immune response, antigen presentation depends on the MHC class II molecule human-leukocyte antigen DR (HLA-DR) and immune depression is characterized by decreased HLA-DR expression on antigen-presenting cells such as monocytes or macrophages. Recently, immune depressed states such as sepsis have been linked to increases in the check point inhibitor programmed cell death protein (PD)-1 and its ligand PD-L1. In neonatal mouse monocytes and AM, we found that in utero ETOH exposure increased immunodepression by increasing oxidant stress, diminishing zinc and GM-CSF, decreasing MHC-II expression, and increasing PD-1/PD-L1. However, GSH or Zinc treatments blocked these effects. In tracheal aspirates of intubated VLBW infants, HLA-DR was diminished in AM from babies who developed LOS while PD-L1 was increased in babies who developed LOS or BPD. In addition, PD- 1 and PD-L1 expressions were increased in AM from VLBW infants with in utero alcohol exposure compared to unexposed AM. Using established in utero ETOH mouse models plus translational studies of VLBW newborns, our overall objectives are to: 1) define in utero ETOH effects on innate and adaptive immune defenses of monocytes, monocyte-derived macrophages (MDM), and AM against bacterial challenges; 2) determine if clinically relevant interventions to diminish oxidant stress (GSH, GM-CSF and Zinc) will improve innate and adaptive responses; 3) validate ethanol metabolites Fatty Acid Ethyl Esters (FAEEs) and phosphatidylethanol (PEth) as biomarkers of in utero alcohol exposure in VLBW newborns and 4) determine phenotype plus innate and adaptive defenses of human monocyte, MDM, and AM samples from VLBW newborns with/without fetal alcohol exposure. Improving identification of VLBW newborns with fetal alcohol exposure and understanding its immunodepressive effects superimposed on immature immune defenses related to prematu...