Interleukin-7 receptor blockade suppresses adaptive and innate inflammatory responses in experimental colitis.
BACKGROUND
Interleukin-7 (IL-7) acts primarily on T cells to promote their differentiation, survival, and homeostasis. Under disease conditions, IL-7 mediates inflammation through several mechanisms and cell types. In humans, IL-7 and its receptor (IL-7R) are increased in diseases characterized by inflammation such as atherosclerosis, rheumatoid arthritis, psoriasis, multiple sclerosis, and inflammatory bowel disease. In mice, overexpression of IL-7 results in chronic colitis, and T-cell adoptive transfer studies suggest that memory T cells expressing high amounts of IL-7R drive colitis and are maintained and expanded with IL-7. The studies presented here were undertaken to better understand the contribution of IL-7R in inflammatory bowel disease in which colitis was induced with a bacterial trigger rather than with adoptive transfer.


METHODS
We examined the contribution of IL-7R on inflammation and disease development in two models of experimental colitis: Helicobacter bilis (Hb)-induced colitis in immune-sufficient Mdr1a-/- mice and in T- and B-cell-deficient Rag2-/- mice. We used pharmacological blockade of IL-7R to understand the mechanisms involved in IL-7R-mediated inflammatory bowel disease by analyzing immune cell profiles, circulating and colon proteins, and colon gene expression.


RESULTS
Treatment of mice with an anti-IL-7R antibody was effective in reducing colitis in Hb-infected Mdr1a-/- mice by reducing T-cell numbers as well as T-cell function. Down regulation of the innate immune response was also detected in Hb-infected Mdr1a-/- mice treated with an anti-IL-7R antibody. In Rag2-/- mice where colitis was triggered by Hb-infection, treatment with an anti-IL-7R antibody controlled innate inflammatory responses by reducing macrophage and dendritic cell numbers and their activity.


CONCLUSIONS
Results from our studies showed that inhibition of IL-7R successfully ameliorated inflammation and disease development in Hb-infected mice by controlling the expansion of multiple leukocyte populations, as well as the activity of these immune cells. Our findings demonstrate an important function of IL-7R-driven immunity in experimental colitis and indicate that the therapeutic efficacy of IL-7R blockade involves affecting both adaptive and innate immunity.
Department of Inflammation, Amgen, Inc, Seattle, WA, USA.
Cynthia R
CR
Willis
Department of Comparative Medicine, University of Washington, Seattle, WA, USA.
Audrey
A
Seamons
Department of Inflammation, Amgen, Inc, Seattle, WA, USA.
Joe
J
Maxwell
Department of Comparative Medicine, University of Washington, Seattle, WA, USA.
Piper M
PM
Treuting
Department of Inflammation, Amgen, Inc, Seattle, WA, USA.
Laurel
L
Nelson
Department of Inflammation, Amgen, Inc, Seattle, WA, USA.
Guang
G
Chen
Department of Comparative Medicine, University of Washington, Seattle, WA, USA.
Susan
S
Phelps
Department of Inflammation, Amgen, Inc, Seattle, WA, USA.
Carole L
CL
Smith
Department of Comparative Medicine, University of Washington, Seattle, WA, USA.
Thea
T
Brabb
Department of Comparative Medicine, University of Washington, Seattle, WA, USA.|Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
Brian M
BM
Iritani
Department of Comparative Medicine, University of Washington, Seattle, WA, USA.
Lillian
L
Maggio-Price