MIF homologues from a filarial nematode parasite synergize with IL-4 to induce alternative activation of host macrophages

Macrophage migration inhibitory factor (MIF) is a highly conserved cytokine considered to exert wide-ranging, proinflammatory effects on the immune system. Recently, members of this gene family have been discovered in a number of invertebrate species, including parasitic helminths. However, chronic helminth infections are typically associated with a Th2-dominated, counter-inflammatory phenotype, in which alternatively activated macrophages (AAMs) are prominent. To resolve this apparent paradox, we have analyzed the activity of two helminth MIF homologues from the filarial nematode Brugia malayi, in comparison with the canonical MIF from the mouse. We report that murine MIF (mMIF) and Brugia MIF proteins induce broadly similar effects on bone marrow-derived mouse macrophages, eliciting a measured release of proinflammatory cytokines. In parallel, MIF was found to induce up-regulation of IL-4R on macrophages, which when treated in vitro with MIF in combination with IL-4, expressed markers of alternative activation [arginase, resistin-like molecule α (RELM-α) or found in inflammatory zone 1, Ym-1, murine macrophage mannose receptor] and differentiated into functional AAMs with in vitro-suppressive ability. Consistent with this finding, repeated in vivo administration of Brugia MIF induced expression of alternative macrophage activation markers. As mMIF did not induce RELM-α or Ym-1 in vivo, alternative activation may require components of the adaptive immune response to Brugia MIF, such as the production of IL-4. Hence, MIF may accentuate macrophage activation according to the polarity of the environment, thus promoting AAM differentiation in the presence of IL-4-inducing parasitic helminths

Structural and functional studies on ø29 DNA polymerase

The Bac i l lus subtilis phage 029 DNA polymerase, involved in protein-primed viral DNA repli- cation, contains several amino acid consensus sequences common to other eukaryotic-type DNA polymerases. Us- ing site-directed mutagenesis, we have studied the func- tional significance o f a C-terminal conserved region, rep- resented by the Lys-X-Tyr ("K-Y") motif. Single point mutants have be en constructed and the corresponding proteins have been overproduced and characterized. Measurements o f the activity o f the mutant proteins indi- cated that the invariant Lys and Tyr residues play a criti- cal role in DNA polymerization. Interestingly, substitu- tion o f the invariant Lys either by Arg or Thr, produced enzymes with an increased or a largely reduced, respec- tively, capability to use a protein as primer, an intrinsic property o f TP-priming DNA polymerases. On the other hand, the viral protein p6, whi ch stimulates initiation o f 029 DNA replication by formation o f a nucleoprotein complex at both DNA replication origins, increased (about 5-fold) the insertion fidelity o f 029 DNA polymerase during the formation o f the TP-dAMP initia- tion complex. We propose a mode l in whi ch the special strategy to maintain the integrity o f the 029 DNA ends, by means o f a "sliding-back" mechanism, could also con- tribute to increase the fidelity o f 029 DNA replication.This investigation has been aided byreseareh grant 5R01 GM27242-13 from the National Institutes o f Health, by grant n ~ PB90-0091 from Direccibn General de Investigacibn Cientifica y T6c- nica, by grant BlOT CT 91-0268 from European Economic Commani- ty, and by an institutional grant from Fundaci6n Ram6n Areces. M.A.B., J.A.E. and J.M., were predoctoral fellows from Ministerio de Educaci6n y Ciencia.Peer reviewe

Crosstalk between sentinel and helper macrophages permits neutrophil migration into infected uroepithelium

The phagocytes of the innate immune system, macrophages and neutrophils, contribute to antibacterial defense, but their functional specialization and cooperation is unclear. Here, we report that three distinct phagocyte subsets play highly coordinated roles in bacterial urinary tract infection. Ly6C(-) macrophages acted as tissue-resident sentinels that attracted circulating neutrophils and Ly6C(+) macrophages. Such Ly6C(+) macrophages played a previously undescribed helper role: once recruited to the site of infection, they produced the cytokine TNF, which caused Ly6C(-) macrophages to secrete CXCL2. This chemokine activated matrix metalloproteinase-9 in neutrophils, allowing their entry into the uroepithelium to combat the bacteria. In summary, the sentinel macrophages elicit the powerful antibacterial functions of neutrophils only after confirmation by the helper macrophages, reminiscent of the licensing role of helper T cells in antiviral adaptive immunity. These findings identify helper macrophages and TNF as critical regulators in innate immunity against bacterial infections in epithelia.publisher: Elsevier articletitle: Crosstalk between Sentinel and Helper Macrophages Permits Neutrophil Migration into Infected Uroepithelium journaltitle: Cell articlelink: http://dx.doi.org/10.1016/j.cell.2014.01.006 content_type: article copyright: Copyright © 2014 Elsevier Inc. All rights reserved.status: publishe

Homologues of human macrophage migration inhibitory factor from a parasitic nematode gene cloning protein activity and crystal structure

Cytokines are the molecular messengers of the vertebrate immune system, coordinating the local and systemic immune responses to infective organisms. We report here functional and structural data on cytokine-like proteins from a eukaryotic pathogen. Two homologues of the human cytokine macrophage migration inhibitory factor (MIF) have been isolated from the parasitic nematode Brugia malayi. Both molecules (Bm-MIF-1 and Bm-MIF-2) show parallel functions to human MIF. They are chemotactic for human monocytes and activate them to produce IL-8, TNF-alpha, and endogenous MIF. The human and nematode MIF homologues share a tautomerase enzyme activity, which is in each case abolished by the mutation of the N-terminal proline residue. The crystal structure of Bm-MIF-2 at 1.8-A resolution has been determined, revealing a trimeric assembly with an inner pore created by beta-stranded sheets from each subunit. Both biological activity and crystal structure reveal remarkable conservation between a human cytokine and its parasite counterpart despite the considerable phylogenetic divide among these organisms. The strength of the similarity implies that MIF-mediated pathways play an important role in nematode immune evasion strategies