Th-1 polarization towards interferon-γ production, and monocyte activation to TNF-α secretion, are triggered in the mesenteric lymphoid system by bacteria in cirrhotic rats with ascites.

Abstract

The ontogeny of the intestinal immune system is dependent on bacterial flora. Moreover, lymphocytes specific against the sapro- phitic enteric flora are expanded in the mesenteric lymphoid organs. Bacterial translocation from the intestinal lumen into the draining mesenteric lymph nodes (MLN) is a hallmark of cirrhosis with ascites. We have experimentally addressed whether a strong T and B cell, and monocyte immune response against enteric bacteria occurs in CC14 cirrhotic rats with ascites. In Protocol I, the immune cell phenotype, activation status, and polarization in the cytokine produced were assayed by four-color immunofluores- cence and quantitative flow cytometry. In Protocol 11, the contri- bution of gut bacteria to the immune disturbance was addressed by intestinal bacterial decontamination. Results: (mean5SD): In Protocol I, the MLN of cirrhotic rats shows expansion of T (1.5- fold) and B cells (3-fold) and monocytes (6-fold). Activated Th cells accounted for most of the T-cell expansion in the MLN of cirrhotic rats compared to control rats (861000~414000 vs. 122OOOrt-55000 CD4+CD134+ cellslnode, p<O.Ol). Activated Th cells are known to leave the MLN, which is consistent with their increased number in the blood of cirrhotic rats (22OOOrt-12000 vs. 4800?1000 cellslpl, p<O.Ol). That activated Th cells selectively origin in the MLN of cirrhotic rats was revealed by: i) the lack of expansion of this population in the axilary lymph nodes, ii) the direct correlation among their numbers in MLN and blood (r=0.66, p<O.Ol), and iii) the expansion in MLN, but not in blood or axilary nodes, of activated Th cells that lack the CD45RC receptor, which are un- able to re-enter lymph nodes. Activated Th cells do produce interferon-y in MLN (5.623 vs. 0.42?0.2%, p<O.Ol) and blood of cirrhotic rats. Interferon-y is the prototype cytokine in Th-1 po- larization, and a known promoter of TNF-a production by mono- cytes. In cirrhotic rats, monocytes from MLN (52528 vs. 2.4t1.5”/,, p<O.Ol) and blood, but not T-cells, are spontaneously activated to TNF-LU production. In Protocol 11, bowel decontamination of cir- rhotic rats with broad-spectrum non-absorbable antibiotics abro- gated the fecal aerobic bacterial load, reduced bacterial translocation to MLN (60 vs. 8%, p<0.05), decreased the number of CD134+ and of CD45RC- Th cells in MLN, and normalized the production of TNF-a by monocytes and interferon-g by Th cells both in MLN and blood. Conclusions: In cirrhosis, enteric bacteria initiate an orchestrated immune response cascade in which MLN T cells are polarized to a Th-1 profile, and monocytes activated to TNF-LU production. Recirculation of MLN activated effector im- mune cells later promotes systemic inflammation. (Resumen de aportación publicado en: (2004), AASLD Abstract (pp. 162A–266A). Hepatology, 40: 574A-675A. https://doi.org/10.1002/hep.1840400507)