M2b Monocytes Provoke Bacterial Pneumonia and Gut Bacteria-Associated Sepsis in Alcoholics.

Chronic alcohol consumption markedly impairs host antibacterial defense against opportunistic infections. γ-irradiated NOD-SCID IL-2Rγ(null) mice inoculated with nonalcoholic PBMCs (control PBMC chimeras) resisted Klebsiella pneumonia and gut bacteria-associated sepsis, whereas the chimeras created with alcoholic PBMCs (alcoholic PBMC chimeras) were very susceptible to these infections. M1 monocytes (IL-12(+)IL-10(-)CD163(-)CD14(+) cells), major effector cells in antibacterial innate immunity, were not induced by a bacterial Ag in alcoholic PBMC cultures, and M2b monocytes (CCL1(+)CD163(+)CD14(+) cells), which predominated in alcoholic PBMCs, were shown to be inhibitor cells on the Ag-stimulated monocyte conversion from quiescent monocytes to M1 monocytes.