Partial depletion of regulatory T cells does not influence the inflammation caused by high dose hemi-body irradiation

PLoS One. 2013;8(2):e56607. doi: 10.1371/journal.pone.0056607. Epub 2013 Feb 11.

Abstract

There is clinical interest in the modulation of regulatory T cells for cancer therapy. The safety of these therapies in combination with conventional anti-cancer therapies, including radiation therapy, can be studied in animal models. The effects of partial depletion of regulatory T (Treg) cells with an anti-CD25 antibody in conjunction with ionizing radiation on inflammation and tissue injury were analyzed in C57BL/6 mice. An anti-CD25 antibody (PC61) was administered 3 days prior to 13 Gy lower-half hemi-body irradiation (HBI). The blood, spleen, mesenteric lymph nodes (mLNs) and inguinal lymph nodes (iLNs) were harvested at various times thereafter. Alterations in the proportion of leukocyte subsets including CD4(+) T cells, CD8(+) T cells, Treg cells, B cells, NK cells, NK1.1(+) T cells, macrophages and granulocytes were analyzed by FACS. The lungs, liver, pancreas, stomach, jejunum, duodenum, ileum, colon and kidney were harvested and studied by H&E staining. Expression of inflammatory mediators in plasma and tissue were investigated by ELISA. HBI significantly decreased the leukocyte pool though the various leukocyte subsets had different sensitivities to HBI. The administration of PC61 significantly decreased the proportion of Treg cells in spleen, iLN, mLN and blood (reduction of approximately 60%). Irradiation significantly increased the proportion of Treg cells in the spleen, iLN and mLN. HBI induced a systemic inflammatory reaction as demonstrated by increased plasma levels of IL-6, KC/CXCL1 and circulating granulocytes in the blood. Neutrophils also infiltrated the small bowel. The same general patterns were observed whether or not Treg cells were partially depleted with PC61 prior to HBI. These data demonstrate that partial depletion of Treg cells in these mice does not influence HBI-induced inflammatory response and tissue injury, and that combining anti-CD25 therapy with radiation may be safe and well tolerated in a clinical setting.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal / immunology
  • Biomarkers / metabolism
  • Cell Count
  • Female
  • Hemibody Irradiation / adverse effects*
  • Inflammation / etiology*
  • Inflammation / immunology
  • Inflammation / metabolism
  • Inflammation / pathology
  • Interleukin-2 Receptor alpha Subunit / immunology
  • Mice
  • Mice, Inbred C57BL
  • Radiation Dosage*
  • Radiation Injuries / immunology*
  • Radiation Injuries / metabolism
  • Radiation Injuries / pathology
  • T-Lymphocytes, Regulatory / cytology*
  • T-Lymphocytes, Regulatory / immunology
  • T-Lymphocytes, Regulatory / radiation effects*

Substances

  • Antibodies, Monoclonal
  • Biomarkers
  • Interleukin-2 Receptor alpha Subunit

Grant support

The work was supported by The Horchow Foundation, the Department of Radiation Oncology and the Cancer Immunobiology Center, University of Texas Southwestern Medical Center. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.