RESUMO
Natural killer (NK) cells play critical roles in antiviral immunity. While the importance of effector mechanisms such as interferons has been demonstrated through knockout mice, specific mechanisms of how viruses are recognized and controlled by NK cells are less well defined. Previous genetic studies have mapped the resistance genes for murine cytomegalovirus (MCMV), herpes simplex virus-1 (HSV-1), and ectromelia virus to the NK gene complex on murine chromosome 6, a region containing the polymorphic Ly49 and Nkrp1 families. Genetic resistance to MCMV in C57BL/6 has been attributed to Ly49H, an activation receptor, through susceptibility of the recombinant inbred strain BXD-8 that lacks Ly49h (also known as Klra8) but derived about half of its genome from its DBA/2 progenitor. However, it remained possible that epigenetic effects could account for the MCMV phenotype in BXD-8 mice. Herein, we report the generation of a novel congenic murine strain, B6.BXD8-Klra8 ( Cmv1-del )/Wum, on the C57BL/6 genetic background to evaluate the effect of deletion of a single NK activation receptor, Ly49H. Deletion of Ly49H rendered mice much more susceptible to MCMV infection. This increase in susceptibility did not appear to be a result of a difference in NK cell expansion or interferon-gamma (IFN-gamma) production between the C57BL/6 and the B6.BXD8 strains. On the other hand, the deletion of Ly49h did not otherwise affect NK cell maturation or Ly49D expression and had no effect on susceptibility to HSV-1 or ectromelia virus. In conclusion, Ly49h is necessary for genetic resistance to MCMV, but not HSV-1 or ectromelia virus.
Assuntos
Infecções por Citomegalovirus/virologia , Muromegalovirus/patogenicidade , Subfamília A de Receptores Semelhantes a Lectina de Células NK/fisiologia , Animais , Southern Blotting , Infecções por Citomegalovirus/genética , Infecções por Citomegalovirus/imunologia , Feminino , Citometria de Fluxo , Genótipo , Herpes Simples/genética , Herpes Simples/imunologia , Herpes Simples/virologia , Herpesvirus Humano 1/genética , Herpesvirus Humano 1/imunologia , Herpesvirus Humano 1/patogenicidade , Células Matadoras Naturais , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Repetições de Microssatélites , Muromegalovirus/genética , Muromegalovirus/imunologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Taxa de SobrevidaRESUMO
Natural interferon-producing cells (IPC) respond to viruses by secreting type I interferon (IFN) and interleukin-12 (IL-12). Toll-like receptor (TLR) 9 mediates IPC recognition of some of these viruses in vitro. However, whether TLR9-induced activation of IPC is necessary for an effective antiviral response in vivo is not clear. Here, we demonstrate that IPC and dendritic cells (DC) recognize murine cytomegalovirus (MCMV) through TLR9. TLR9-mediated cytokine secretion promotes viral clearance by NK cells that express the MCMV-specific receptor Ly49H. Although depletion of IPC leads to a drastic reduction of the IFN-alpha response, this allows other cell types to secrete IL-12, ensuring normal IFN-gamma and NK cell responses to MCMV. We conclude that the TLR9/MyD88 pathway mediates antiviral cytokine responses by IPC, DC, and possibly other cell types, which are coordinated to promote effective NK cell function and MCMV clearance.