Anti-TREM1 monoclonal antibody, clone TREM-37

CD103(+)CD11b(+) dendritic cells (DCs) are unique to the intestine, but the factors governing their differentiation are unclear. Here we show that transforming growth factor receptor 1 (TGF beta beta R1) has an indispensable, cell intrinsic role in the development of these cells. Deletion of Tgfbr1 results in markedly fewer intestinal CD103(+)CD11b(+) DCs and a reciprocal increase in the CD103(-)CD11b(+) dendritic cell subset. Transcriptional profiling identifies markers that define the CD103(+)CD11b(+) DC lineage, including CD101, TREM1 and Siglec-F, and shows that the absence of CD103(+)CD11b(+) DCs in CD11c-Cre. Tgfbr1(fl/fl) mice reflects defective differentiation from CD103(-)CD11b(+) intermediaries, rather than an isolated loss of CD103 expression. The defect in CD103(+)CD11b(+) DCs is accompanied by reduced generation of antigen-specific, inducible FoxP3(+) regulatory T cells in vitro and in vivo, and by reduced numbers of endogenous Th17 cells in the intestinal mucosa. Thus, TGF beta R1-mediated signalling may explain the tissue-specific development of these unique DCs.

During bacterial infection, activated polymorphonuclear leukocytes (PMNs) often cause inflammation and organ dysfunction in severely ill patients. Gene expression was analyzed in circulating PMNs isolated from these patients to determine the distinct expression profile. We focused on immunomodulatory genes, such as those for pattern recognition receptors, inflammatory cytokines, PMN surface antigens, and myeloid cell receptors in PMNs. Gene expression in 23 patients (12 with pneumonia and 11 with sepsis) were analyzed using quantitative real-time polymerase chain reaction. The mRNA levels of TLR2 (20/23 cases) and CD14 (18/23 cases) were upregulated in the PMNs of patients when compared with healthy subjects. The mRNA expression levels of TLR4 (16/23 cases) and IL6 (16/23 cases) were downregulated in patients' PMNs, and of TNFA (16/23 cases) were upregulated in these cells. Although mRNA levels of IL8RA (15/23 cases) were downregulated in PMNs, MAC-1 mRNA levels (14/23 cases) were upregulated in the same cells. Copies of the TREM1 transcript were 0.7- to 2.1-fold higher in patients with moderate pneumonia than in the healthy subjects; the average fold change was 1.1. The mRNA levels were 0.3-fold lower in the patients with severe pneumonia and sepsis than in the healthy subjects. In conclusion, the downregulation of TREM1 expression in PMNs is associated with the severity of the pathophysiological conditions and may be used as a surrogate marker of acute bacterial infections.