Open Access

ARTICLE

Effect of age on homeostasis of lymphocytes in an interleukin-7-deficient mouse model

Astrid Stienen^1,2, Oliver Feyen¹, Tim Niehues^1,3

1 Department of Pediatric Oncology, Hematology and Immunology, University Children’s Hospital Duesseldorf
2 Department of Pediatrics, University Hospital RWTH Aachen, Aachen
3 Department of Pediatrics, Helios Hospital Krefeld, Krefeld, Germany

* Corresponding Author: T. Niehues,

European Cytokine Network 2011, 22(1), 63-72. https://doi.org/10.1684/ecn.2011.0273

Accepted 18 January 2010;

Abstract

Interleukin (IL)-7 is thought to be a non-redundant cytokine for lymphopoiesis as there is a reduction of T and B cells in peripheral blood (PB) and a loss of TCRγδ⁺ cells in PB and bone marrow (BM) in IL-7^-/- mice. To investigate whether the absence of IL-7 influences the organ-dependent distribution of the lymphocytes, we analyzed single cell suspensions of several organs (BM, lung, liver, small intestine, and spleen) at different ages (three and 12 months) of IL-7^+/+ and IL-7^-/- mice using flow cytometry; immunohistochemical staining was performed on frozen sections of various organs. We observed lymphocytopenia in almost all organs of IL-7^-/- mice, but normal counts in the liver and the lung of three-month-old IL-7^-/- mice. CD4⁺ and CD8⁺ cell numbers were decreased in the spleen and the BM. With aging, we found a greater increase in CD4⁺ and CD8⁺ cells in the BM of IL-7^-/- than in IL-7^+/+ mice, particularly of memory cells. The spleen of IL-7^-/- mice was characterized by lymphocytopenia. We challenge the view that IL-7 is a non-redundant cytokine for lymphocyte development. Some of the changes observed, e.g. partial absence of TCRγδ⁺ T cells in the PB, BM and small intestine and complete loss in liver, lung and spleen, may be due to the altered organ distribution instead of a defect in γδ⁺ T cell lymphopoiesis. In this model, aging leads to a significantly altered composition of lymphocyte subsets, and the lack of IL-7 seems to accelerate this process.

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