Tolerance and Cross-Tolerance following Toll-Like Receptor (TLR)-4 and -9 Activation Are Mediated by IRAK-M and Modulated by IL-7 in Murine Splenocytes

• Published in: PloS one Vol. 10; no. 7; p. e0132921
• Main Authors: Julian, Mark W, Strange, Heather R, Ballinger, Megan N, Hotchkiss, Richard S, Papenfuss, Tracey L, Crouser, Elliott D
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 28.07.2015; Public Library of Science (PLoS)
• Subjects: Analysis; Animals; Blocking antibodies; Critical care; Cross-tolerance; Cytokines; Cytomegalovirus; Deoxyribonucleic acid; DNA; Drug dosages; Enzyme-linked immunosorbent assay; Hazards; Health aspects; House mouse; Illnesses; Immune response; Immune system; Immune Tolerance; Immunological tolerance; In vivo methods and tests; Infection; Infections; Inflammation; Interferon-gamma - genetics; Interferon-gamma - immunology; Interleukin 10; Interleukin 7; Interleukin-1 Receptor-Associated Kinases - genetics; Interleukin-1 Receptor-Associated Kinases - immunology; Interleukin-10 - genetics; Interleukin-10 - immunology; Interleukin-7 - genetics; Interleukin-7 - immunology; Laboratory animals; Ligands; Lipopolysaccharides; Lipopolysaccharides - pharmacology; Lymphocytes; Male; Mice; Mice, Knockout; Mitochondrial DNA; Mycobacterium tuberculosis; Oligodeoxyribonucleotides - pharmacology; PD-1 protein; Proteins; Rodents; Sepsis; Signal transduction; Sleep; Spleen - cytology; Spleen - immunology; Splenocytes; Toll-Like Receptor 4 - genetics; Toll-Like Receptor 4 - immunology; Toll-Like Receptor 9 - genetics; Toll-Like Receptor 9 - immunology; Toll-like receptors; Tuberculosis; Tumor Necrosis Factor-alpha - genetics; Tumor Necrosis Factor-alpha - immunology; Tumor necrosis factor-α; Veterinary colleges; Veterinary medicine; Viral infections; Viruses; γ-Interferon
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0132921

Immune suppression during critical illness predisposes to serious infections. We sought to determine the mechanisms regulating tolerance and cross-tolerance to common pro-inflammatory danger signals in a model that recapitulates the intact in vivo immune response. Flt3-expanded splenocytes obtained from wild-type or matching IRAK-M knockout (IRAK-M-/-), C57BL/6, male mice (8-10 weeks old) were treated repeatedly or alternately with either LPS or CpGA DNA, agonists of Toll-like receptor (TLR)-4 and -9, respectively, over successive 24-hour periods. Supernatants were collected following each 24-hour period with cytokine release (ELISA) and splenocyte IRAK-M expression (Western blot) determined. Tolerance and cross-tolerance were assessed in the absence or presence of programmed death receptor (PD)-1 blocking antibody or IL-7 pre-treatment. Splenocytes notably exhibited both tolerance and cross-tolerance to subsequent treatments with either LPS or CpGA DNA. The character of tolerance and cross-tolerance in this model was distinct following initial LPS or CpGA treatment in that TNFα and IFNγ release (not IL-10) were suppressed following LPS; whereas, initial CpGA treatment suppressed TNFα, IFNγ and IL-10 release in response to subsequent stimulation (LPS or CpGA). Tolerance and cross-tolerance were unrelated to IL-10 release or PD-1 but were attenuated in IRAK-M-/- splenocytes. IL-7 significantly suppressed IRAK-M expression and restored TNFα and IFNγ production without influencing IL-10 release. In summary, acute immune tolerance and cross-tolerance in response to LPS or CpGA were distinct in that LPS selectively suppressed pro-inflammatory cytokine responses; whereas, CpGA suppressed both pro- and anti-inflammatory responses. The induction of tolerance and cross-tolerance in response to common danger signals was mechanistically unrelated to IL-10 or PD-1 but was directly influenced by IRAK-M expression. IL-7 reduced IRAK-M expression and attenuated immune tolerance induced by either LPS or CpGA, and thus may be useful for reversal of immune tolerance in the setting of critical illness.