CRIg-expressing peritoneal macrophages are associated with disease severity in patients with cirrhosis and ascites.

Infections are an important cause of morbidity and mortality in patients with decompensated cirrhosis and ascites. Hypothesizing that innate immune dysfunction contributes to susceptibility to infection, we assessed ascitic fluid macrophage phenotype and function. The expression of complement receptor of the immunoglobulin superfamily (CRIg) and CCR2 defined two phenotypically and functionally distinct peritoneal macrophage subpopulations.

The E3 ubiquitin ligase RNF144B is LPS-inducible in human, but not mouse, macrophages and promotes inducible IL-1β expression.

Differences in human and mouse immune responses may partly reflect species-specific adaptations and can provide important insights into human immunity. In this study, we show that RNF144B, which encodes an E3 ubiquitin ligase, was lipopolysaccharide-inducible in primary human macrophages and in human macrophage-like THP-1 cells. In contrast, Rnf144b was not lipopolysaccharide-inducible in several mouse cell populations, including primary macrophages from C57BL/6 and BALB/c mice and RAW264.

Histone Deacetylase Inhibitors Promote Mitochondrial Reactive Oxygen Species Production and Bacterial Clearance by Human Macrophages.

Broad-spectrum histone deacetylase inhibitors (HDACi) are used clinically as anticancer agents, and more isoform-selective HDACi have been sought to modulate other conditions, including chronic inflammatory diseases. Mouse studies suggest that HDACi downregulate immune responses and may compromise host defense. However, their effects on human macrophage antimicrobial responses are largely unknown.

Inflammatory responses induced by lipopolysaccharide are amplified in primary human monocytes but suppressed in macrophages by complement protein C5a.

Monocytes and macrophages are important innate immune cells equipped with danger-sensing receptors, including complement and Toll-like receptors. Complement protein C5a, acting via C5aR, is shown in this study to differentially modulate LPS-induced inflammatory responses in primary human monocytes versus macrophages. Whereas C5a enhanced secretion of LPS-induced IL-6 and TNF from primary human monocytes, C5a inhibited these responses while increasing IL-10 secretion in donor-matched human monocyte-derived macrophages differentiated by GM-CSF or M-CSF.

Differences in the repertoire, regulation and function of Toll-like Receptors and inflammasome-forming Nod-like Receptors between human and mouse.

Ilya Metchnikoff's use of starfish larvae to discover phagocytosis, and Bruno Lemaitre's and Jules Hoffmann's identification of host defence functions for Drosophila Toll provide compelling examples of the utility of model organisms for discovery of human innate immune pathways. Bruce Beutler's mapping of lipopolysaccharide non-responsiveness in C3H/HeJ mice to the Toll-like Receptor 4 gene similarly highlights the power of the mouse as a model. Models have limitations however, and characterising the functional relevance of human innate immune responses not conserved in the mouse presents both a challenge and an opportunity.

The mammalian DUF59 protein Fam96a forms two distinct types of domain-swapped dimer.

Fam96a mRNA, which encodes a mammalian DUF59 protein, is enriched in macrophages. Recombinant human Fam96a forms stable monomers and dimers in solution. Crystal structures of these two forms revealed that each adopts a distinct type of domain-swapped dimer, one of which is stabilized by zinc binding.