Grant Gallagher

IFN-λs mediate antiviral protection through a distinct class II cytokine receptor complex

We report here the identification of a ligand-receptor system that, upon engagement, leads to the establishment of an antiviral state. Three closely positioned genes on human chromosome 19 encode distinct but paralogous proteins, which we designate interferon-λ1 (IFN-λ1), IFN-λ2 and IFN-λ3 (tentatively designated as IL-29, IL-28A and IL-28B, respectively, by HUGO). The expression of IFN-λ mRNAs was inducible by viral infection in several cell lines. We identified a distinct receptor complex that is utilized by all three IFN-λ proteins for signaling and is composed of two subunits, a receptor designated CRF2-12 (also designated as IFN-λR1) and a second subunit, CRF2-4 (also known as IL-10R2). Both receptor chains are constitutively expressed on a wide variety of human cell lines and tissues and signal through the Jak-STAT (Janus kinases–signal transducers and activators of transcription) pathway. This receptor-ligand system may contribute to antiviral or other defenses by a mechanism similar to, but independent of, type I IFNs.

IFN-λ1 (IL-29) inhibits GATA3 expression and suppresses Th2 responses in human naive and memory T cells

IFN-lambda1 (IL-29) plays a novel, emerging role in the inhibition of human Th2 responses. Here, we demonstrate that both naive and memory human CD4(+) T cells express mRNA for the IFN-lambda1-specific receptor, IL-28Ralpha, and are responsive to IFN-lambda1. Expression of Th2 cytokines (IL-4 and IL-13) was suppressed in naive and memory CD4(+) T cells by IFN-lambda1, without affecting their proliferation. Further, acquisition of IL-4Ralpha expression after stimulation was inhibited by IFN-lambda1, as was GATA3 expression. Finally, IFN-lambda1 diminished the change in cell-surface phenotype that accompanies differentiation of central memory T cells into effector memory T cells. Taken together, our data describe unique immunomodulatory effects of IFN-lambda1 and identify novel mechanisms for the reduction of existing Th2 responses and the regulation of new ones, in circulating naive and memory CD4(+) T cells.

Modulation of human plasmacytoid DC function by IFN-λ1 (IL-29)

The type III family of IFNs displays immunomodulatory and antiviral activity. Each member (IFN‐λ1, −2, and −3) signals through the same heterodimeric receptor complex, which consists of the binding and signaling subunit (IL‐28Rα) plus the IL‐10Rβ chain. Although the receptor has a wide tissue distribution, the direct effects of IFN‐λ on various immune cell subsets have not been fully characterized. We have identified high levels of IL‐28Rα mRNA in pDC from peripheral blood and hypothesized that IFN‐λ plays an important role in pDC maturation and development. We show that stimulation of pDC with HSV or Imiquimod causes an increase in IL‐28Rα mRNA. In these cells, IFN‐λ1 alters expression of the costimulatory molecules CD80 and ICOS‐L and synergizes with IFN‐α to up‐regulate CD83. In addition, IFN‐λ1 has a variable effect on the homing molecule expression of pDC and mDC. IFN‐λ1‐treated pDC display a marked difference in their ability to stimulate production of the signature cytokines IL‐13, IFN‐γ, and IL‐10 in a MLR. This work characterizes the variable effects of IFN‐λ on DC surface molecule expression and identifies a role in pDC activation and immunostimulatory potential.

Interferon‐λ1 (interleukin‐29) preferentially down‐regulates interleukin‐13 over other T helper type 2 cytokine responses in vitro

Interferon (IFN)‐λ1 [interleukin (IL)‐29] is a member of the interferon lambda family (also known as type III interferons), whose members are distantly related to both the type I interferons and members of the IL‐10 family. While IFN‐λ1 has significant antiviral activity, it is also becoming apparent that it has important immunoregulatory properties, especially with regard to the T helper type 2 (Th2) response. Previously, we have shown that IFN‐λ1 is capable of down‐regulating IL‐13 production in an IFN‐γ‐independent manner and that this is mediated in part via monocyte‐derived dendritic cells. Here, we have extended our knowledge of IFN‐λ1 regulation of the human in vitro Th2 response by examining the regulation of three major Th2 cytokines, IL‐4, IL‐5 and IL‐13, by IFN‐λ1. Our results reveal that IFN‐λ1 preferentially inhibits IL‐13 production, compared with IL‐4 or IL‐5. Levels of IL‐13 mRNA, the amount of secreted IL‐13 protein and numbers of IL‐13‐positive CD3+u2003CD4+ cells were all significantly diminished by IFN‐λ1. IFN‐λ1 significantly decreased some aspects of IL‐4 and IL‐5 production, but its effects were not as consistent as those seen on IL‐13. IFN‐λ1 was also effective at decreasing IL‐13 secretion under conditions designed to support the generation of Th2 cells. Irrespective of whether Concanavalin‐A or T‐cell‐stimulatory microbeads were used, IFN‐λ1 markedly diminished IL‐13 secretion in cultures where IL‐4 had been added. Thus, IFN‐λ1 appears to be an inhibitor of human Th2 responses whose action is primarily directed towards IL‐13 but which may also affect Th2 responses generally and does not invoke a complementary elevation of IFN‐γ secretion.

Human β-Defensin 2 Induces a Vigorous Cytokine Response in Peripheral Blood Mononuclear Cells

ABSTRACT β-Defensins are a family of small cationic peptides involved in the innate response to microbial infection. Although their role in microbial killing is well established, the mechanisms through which this occurs remain largely undefined. Here, using protein array technology, we describe a role for human β-defensins in the induction of an inflammatory cytokine response by human peripheral blood mononuclear cells (PBMCs). Human β-defensins 1, 2, and 3 were examined for induction of an array of cytokines and chemokines. Some cytokines, such as interleukin 8 (IL-8) and monocyte chemoattractant protein 1, were up-regulated by all three defensins, while others, such as IL-6 and IL-10, were induced more selectively. It was notable that each defensin induced a unique pattern of cytokines. This report documents, for the first time, an analysis of the composite cytokine response of human PBMCs to β-defensins. The induction or up-regulation of a number of cytokines involved in the adaptive immune response suggests a possible role for these defensins in linking innate and acquired immunity.

IL-4 enhances IFN-λ1 (IL-29) production by plasmacytoid DC, via monocyte secretion of IL-1Ra

The type-III interferon (IFN) family is composed of 3 molecules in humans: IFN-lambda1 (interleukin-29 [IL-29]), IFN-lambda2 (IL-28A), and IFN-lambda3 (IL-28B), each of which signals through the same receptor complex. Plasmacytoid dendritic cells (pDCs) are major IFN-lambda producers among peripheral lymphocytes. Recently, it has been shown that IFN-lambda1 exerts a powerful inhibitory effect over the T-helper 2 (Th2) response by antagonizing the effect of IL-4 on CD4(+) T cells and inhibiting the production of Th2-associated cytokines. Here, we asked whether Th2 cytokines exert reciprocal control over IFN-lambda production. IL-4 treatment during stimulation of human peripheral lymphocytes significantly elevated IFN-lambda1 transcription and secretion. However, pDCs were not directly responsive to IL-4. Using depletion and reconstitution experiments, we showed that IL-4-responsive monocytes are an intermediary cell, responding to IL-4 by elevating their secretion of IL-1 receptor antagonist (IL-Ra); this IL-1Ra acts on pDCs to elevate their IFN-lambda1 output. Thus, our experiments revealed a novel mechanism for regulation of both IFN-lambda1 production and pDC function, and suggests an expanded immunomodulatory role for Th2-associated cytokines.