Paired Immunoglobulin-Like Receptor B (PIR-B) Negatively Regulates Macrophage Activation in Experimental Colitis

Abstract

Background & Aims Innate and adaptive immune responses are regulated by crosstalk between activation and inhibitory signals. Dysregulation of the inhibitory signal can lead to aberrant chronic inflammatory diseases such as the inflammatory bowel diseases (IBD). Little is known about negative regulation of innate intestinal immune activation. We examined the role of the inhibitory receptor paired immunoglobulin-like receptor B (PIR-B) in the regulation of macrophage function in innate intestinal immunity. Methods We examined the susceptibility of Pirb-/- and wild-type (WT) mice to dextran sodium sulfate (DSS)-induced colitis. We assessed proinflammatory cytokine release and MAPK and NFκB activation in Pirb-/- and WT macrophages following E. coli stimulation. Macrophage transfer experiments were performed to define the role of PIR-B in the negative regulation of macrophage function in DSS-induced colitis. We also assessed expression of PIR-B human homologs (ILT-2 and ILT-3) in colon biopsy samples from healthy individuals (controls) and patients with IBD. Results Pirb-/- mice had increased susceptibility to DSS-induced colitis. In vitro analysis demonstrated increased production of proinflammatory cytokines (IL-6, IL-1β and TNF-α) and activation of MAPK and NFκB in Pirb-/- macrophages following bacterial activation. Adoptive transfer of bone marrow-derived Pirb-/- macrophages into WT mice was sufficient to increase disease susceptibility. ILT-2 and ILT-3 were expressed on CD68+ and CD68- mononuclear cells and intestinal epithelium in colon biopsy samples from patients and controls. Conclusions PIR-B negatively regulates macrophage functions in response to pathogenic bacteria and chronic intestinal inflammatory responses. Inhibitory receptors such as PIR-B might be used as therapeutic targets for treatment of patients with IBD.

Nanoparticles With Surface Antibody Against CD98 and Carrying CD98 Small Interfering RNA Reduce Colitis in Mice

“…23 We thus tested the cellular uptake of scCD98-functionalized NPs in bone marrow-derived macrophages (BMDMs), which are primary macrophages that have been widely used because of their homogeneity, proliferation capacity, long lifespan, and ease of harvesting. 24, 25 As shown in Supplementary Figure 8, an assessment of cellular uptake at different time points (0, 1, 3, and 6 h) revealed a time-dependent increase in the FITC fluorescence signals of NPs in BMDMs. After 6 h, green fluorescence was mainly detected in the cytoplasm of almost all cells.…”

LILRB receptor-mediated regulation of myeloid cell maturation and function

“…Using a different disease model, PIRB-deficient macrophages similarly demonstrate exacerbated proinflammatory cytokine release and autoimmune colitis [49]. Consistent with the hypothesis that LILRB and PIRB expression on myeloid cells suppresses type-1 inflammatory responses, our laboratory demonstrated that PIRB is necessary to maintain the regulatory phenotype of tumor-infiltrating MDSCs [50].…”

Colonic Eosinophilic Inflammation in Experimental Colitis Is Mediated by Ly6Chigh CCR2+ Inflammatory Monocyte/Macrophage-Derived CCL11

“…Immunofluorescence analysis was performed as previously described (14, 32). In brief, frozen sections were fixed in 10% acetone for 10 min, rinsed in PBS, blocked with 3% goat serum/PBS for 2 h at room temperature (RT) and incubated with primary Ab rat anti-mouse F4/80 (5 µg/ml; Ebioscience; San Diego, CA) in 3% normal goat serum/PBS.…”