Luminal inflammation drives location and function of CD64+ macrophages

Los Cocos Cordoba

Otro; Advanced Course on Mucosal Immunology-Society for Mucosal Immunology; 2018

The intestine contains the largest pool of macrophages in the body that is strategically located underneath the epitelial layer and continuously sampling the lumen. CD64 is a specific marker used to identify murine intestinal macrophages under both steady-state and inflammatory conditions. To evaluate if the location of CD64+ macrophages is dependent on the inflammatory environment, we studied the distribution of CD11b+F4/80+CD64+ cells in colon of control or DSS-induced colitis C57BL/6 mice (whole mount immunofluorescence). We found that CD64+CD11b+ and CD64+ F4/80+ macrophages were distributed around the crypts in the steady-state while clusters of these cells predominated in injured areas with marked tissue desorganization in colitis mice. To address if immune complex (IC) influence the function of CD64+ cells, we studied the production of cytokines and NO using macrophages differentiated from bone marrow of WT donors after the incubation with different stimuli (LPS, Poly(A:U) and the addition of IC (OVA-antiOVA). Upon stimulation, the production of IL-10 and NO increased 8-and 3 fold, respectively. The addition of IC reduced significantly these mediators. Finally, to establish if luminal IC have a similar effect on intestinal macrophages, sorted F4/80+ cells of lamina propia from WT donors were stimulated with opsonized fecal bacteria sorted from control or DSS-treated WT mice. Fecal bacteria (IgG+IgA+) from DSS mice reduced significantly the production of IL-10 whereas triggered the highest production of NO. Together, our results suggest a dynamic balance between homeostatic and inflammatory macrophages that is critical for immune surveillance in the intestinal environment.-