Emma Masteller

T cells require Foxo1 to populate the peripheral lymphoid organs

Forkhead transcription factors play critical roles in leukocyte homeostasis. To study further the immunological functions of Foxo1, we generated mice that selectively lack Foxo1 in T cells (Foxo1flox/flox Lck.cre+conditional knockout mice (cKO)). Although thymocyte development appeared relatively normal, Foxo1 cKO mice harbored significantly increased percentages of mature single positive T cells in the thymus as compared with WT mice, yet possessed smaller lymph nodes and spleens that contained fewer T cells. Foxo1 cKO T cells were not more prone to apoptosis, but instead were characterized by a CD62Llo CCR7lo CD44hi surface phenotype, a poorly populated lymphoid compartment in the periphery, and were relatively refractory to TCR stimulation, all of which were associated with reduced expression of Sell, Klf2, Ccr7, and S1pr1. Thus, Foxo1 is critical for naïve T cells to populate the peripheral lymphoid organs by coordinating a molecular program that maintains homeostasis and regulates trafficking.

Targeting IL-34 in chronic inflammation ☆

A second ligand for colony-stimulating factor-1 receptor (CSF-1R) with distinct biologic activities had long been implicated but not appreciated until the recent discovery of interleukin (IL)-34. IL-34 and CSF-1 signal through this common receptor to mediate the biology of mononuclear phagocytic cells. Aberrant macrophage activation by CSF-1 and/or IL-34 is associated with numerous diseases, and clinical therapies targeting this pathway are being tested. Although IL-34 and CSF-1 have distinct activities under physiologic conditions, they appear functionally redundant in various disease states. Thus, blocking the activity of both might be necessary for maximal efficacy.

Colony-stimulating factor (CSF) 1 receptor blockade reduces inflammation in human and murine models of rheumatoid arthritis

BackgroundCSF-1 or IL-34 stimulation of CSF1R promotes macrophage differentiation, activation and osteoclastogenesis, and pharmacological inhibition of CSF1R is beneficial in animal models of arthritis. The objective of this study was to determine the relative contributions of CSF-1 and IL-34 signaling to CSF1R in RA.MethodsCSF-1 and IL-34 were detected by immunohistochemical and digital image analysis in synovial tissue from 15 biological-naïve rheumatoid arthritis (RA) , 15 psoriatic arthritis (PsA) and 7 osteoarthritis (OA) patients . Gene expression in CSF-1- and IL-34-differentiated human macrophages was assessed by FACS analysis and quantitative PCR. RA synovial explants were incubated with CSF-1, IL-34, control antibody (Ab), or neutralizing/blocking Abs targeting CSF-1, IL-34, or CSF1R. The effect of a CSF1R-blocking Ab was examined in murine collagen-induced arthritis (CIA).ResultsCSF-1 (also known as M-CSF) and IL-34 expression was similar in RA and PsA synovial tissue, but lower in controls (P < 0.05). CSF-1 expression was observed in the synovial sublining, and IL-34 in the sublining and the intimal lining layer. CSF-1 and IL-34 differentially regulated the expression of 17 of 336 inflammation-associated genes in macrophages, including chemokines, extra-cellular matrix components, and matrix metalloproteinases. Exogenous CSF-1 or IL-34, or their independent neutralization, had no effect on RA synovial explant IL-6 production. Anti-CSF1R Ab significantly reduced IL-6 and other inflammatory mediator production in RA synovial explants, and paw swelling and joint destruction in CIA.ConclusionsSimultaneous inhibition of CSF1R interactions with both CSF-1 and IL-34 suppresses inflammatory activation of RA synovial tissue and pathology in CIA, suggesting a novel therapeutic strategy for RA.

THU0042 Colony-Stimulating Factor (CSF) Receptor 1 Blockade Overcomes Overlapping Effects of M-CSF and Interleukin-34 on Myeloid Differentiation and Gene Expression to Reduce Inflammation in Human and Murine Models of Rheumatoid Arthritis

Background Disease activity and response to therapy in RA correlates with changes in synovial macrophage numbers and their products. M-CSF or interleukin (IL)-34 stimulation of their common receptor CSFR1 promotes macrophage differentiation, activation and osteoclastogenesis, but M-CSF and IL-34 play distinct roles in murine development. Pharmacological inhibition of CSFR1 is beneficial in animal models of arthritis but the relative contributions of M-CSF, IL-34 and their receptor to inflammation in rheumatoid arthritis (RA) are unknown. Objectives To determine the roles of M-CSF and IL-34 in huma macrophage activation, and human and murine models of RA. Methods M-CSF, IL-34, and cellular markers were detected by immunohistochemistry and digital image analysis in synovial tissue from 18 biological-naïve RA patients, 14 PsA patients, and 4 controls without inflammatory disease (2 healthy donors and 2 OA patients). Gene expression in M-CSF and IL-34 –differentiated human macrophages was assessed by FACS analysis and q-PCR arrays. RA synovial explants were incubated with M-CSF, IL-34, control antibody (Ab), or a humanized CSFR1-blocking Ab. Prophylactic effects of control and CSFR1-blocking Ab were examined in murine collagen-induced arthritis (CIA). Results Expression of M-CSF and IL-34 was similar in RA and PsA synovial tissue, but lower in controls (p< 0.05). M-CSF expression was restricted to ECs and IL-34 was observed in sublining mononuclear cells and intimal lining layer cells. CXCL5, CXCL6, FN1, COL1A1, COL6A1-2, COL14A1, COL15A1, MMP7, MMP8 and MMP9 mRNA expression was significantly upregulated in macrophages differentiated in M-CSF compared to IL-34, while CXCL7, CXCL9, CXCL10, CXCL11, CXCL12, LAMA1, and MMP2 were downregulated. M-CSF or IL-34 had no effect on RA synovial explant IL-6 production, but anti-CSFR1 Ab dose-dependently reduced IL-6 production. Treatment with anti-CSFR1 Ab in CIA significantly reduced paw swelling and joint destruction. Conclusions M-CSF and IL-34 are expressed in topographically distinct regions of inflamed synovial tissue and differentially effect macrophage capacity to attract inflammatory cells and remodel tissue. Simultaneous inhibition of CSFR1 interactions with both M-CSF and IL-34 suppresses inflammatory activation of RA synovial tissue and pathology in CIA, suggesting a novel therapeutic strategy for RA. Disclosure of Interest S. Garcia: None Declared, L. Hartkamp: None Declared, M. W. Tang: None Declared, I. van Es: None Declared, H. Lin Shareholder of: stock options in Five Prime Therapeutics, Inc., Employee of: Five Prime Therapeutics, Inc., L. Long Shareholder of: stock options in Five Prime Therapeutics, Inc., Employee of: Five Prime Therapeutics, Inc., E. Masteller Shareholder of: stock options in Five Prime Therapeutics, Inc., Employee of: Five Prime Therapeutics, Inc., B. Wong Shareholder of: stock options in Five Prime Therapeutics, Inc., Employee of: Five Prime Therapeutics, Inc., P. Tak Employee of: GlaxoSmithKline, K. Reedquist Grant/research support from: Five Prime Therapeutics, Inc.