A better understanding of immunity to influenza virus is needed to generate cross-protective vaccines. Engagement of Ab-dependent cellular cytotoxicity (ADCC) Abs by NK cells leads to killing of virus-infected cells and secretion of antiviral cytokines and chemokines. ADCC Abs may target more conserved influenza virus Ags compared with neutralizing Abs. There has been minimal interest in influenza-specific ADCC in recent decades. In this study, we developed novel assays to assess the specificity and function of influenza-specific ADCC Abs. We found that healthy influenza-seropositive young adults without detectable neutralizing Abs to the hemagglutinin of the 1968 H3N2 influenza strain (A/Aichi/2/1968) almost always had ADCC Abs that triggered NK cell activation and in vitro elimination of influenza-infected human blood and respiratory epithelial cells. Furthermore, we detected ADCC in the absence of neutralization to both the recent H1N1 pandemic strain (A/California/04/2009) as well as the avian H5N1 influenza hemagglutinin (A/Anhui/01/2005). We conclude that there is a remarkable degree of cross-reactivity of influenza-specific ADCC Abs in seropositive humans. Targeting cross-reactive influenza-specific ADCC epitopes by vaccination could lead to improved influenza vaccines.

No abstract

The ability of the rodent testis to tolerate graft alloantigens and spermatogenic cell autoantigens is well known. The mechanisms underlying this "immune privilege" are poorly understood, but the numerous resident TMs have been implicated. Although it has been assumed that TMs display a phenotype consistent with immune privilege, this has not been formally established. Consequently, TMs were isolated from adult rats and cultured under basal conditions and following stimulation with LPS and IFN-γ (classical activation) or IL-4 (alternative activation). BMMs matured in vitro were used as control. Expression of the classical (proinflammatory) activation markers TNF-α, IL-1β, iNOS, IL-6, RANTES, IL-12p40, and SOCS3 and alternative (immunoregulatory) activation markers IL-10, TGF-β1, CXCL2, and SOCS1 was measured by QPCR or ELISA. In culture, TMs were characterized by poor expression of classical activation genes and TGF-β1 but constitutively high IL-10 production and reduced costimulatory activity in a polyclonal T cell activation assay. This pattern of gene expression was associated with TMs expressing the scavenger receptor CD163, which is characteristic of tissue resident macrophages and alternative activation. By contrast, CD163-negative TMs displayed reduced inflammatory gene expression but did not constitutively produce IL-10. These data indicate that under the influence of the testicular environment, macrophages adopt an alternatively activated phenotype, involving reduced capacity for proinflammatory gene expression, constitutive IL-10 production, and impaired ability to support T cell activation, consistent with a role in maintaining testicular immune privilege.