How the development of antibacterial T helper 17 (Th17) cells is selectively promoted by antigen-presenting dendritic cells (DCs) is unclear. We showed that bacteria, but not viruses, primed human DCs to promote IL-17 production in memory Th cells through the nucleotide oligomerization domain 2 (NOD2)-ligand muramyldipeptide (MDP), a derivative of bacterial peptidoglycan. MDP enhanced obligate bacterial Toll-like receptor (TLR) agonist induction of IL-23 and IL-1, which promoted IL-17 expression in T cells. The role of NOD2 in this IL-23-IL-1-IL-17 axis could be confirmed in NOD2-deficient DCs, such as DCs from selected Crohn's disease patients. Thus, antibacterial Th17-mediated immunity in humans is orchestrated by DCs upon sensing bacterial NOD2-ligand MDP.

M2 macrophages suppress inflammation in numerous disorders, including tumour formation, infection and obesity. However, the exact role of M2 macrophages in the context of several other diseases is still largely undefined. We here show that human M2 macrophages promote inflammation instead of suppressing inflammation on simultaneous exposure to complexed IgG (c-IgG) and TLR ligands, as occurs in the context of diseases such as rheumatoid arthritis (RA). c-IgG-TLR ligand co-stimulation of M2 macrophages selectively amplifies production of pro-inflammatory cytokines TNF-α, IL-1β and IL-6 and promotes Th17 responses, which all play a critical role in RA pathology. Induction of pro-inflammatory cytokines on c-IgG co-stimulation mainly depends on Fc gamma receptor IIa (FcγRIIa), which selectively amplifies cytokine gene transcription and induces caspase-1 activation. These data indicate that FcγR-TLR cross-talk may be targeted for treatment to attenuate inflammation in RA, by restoring the anti-inflammatory function of M2 macrophages.

IntroductionProtection against different classes of pathogens requires the activation of Ag-presenting dendritic cells (DCs) to express factors that promote the development of distinct effector Th-cell subsets, which are specialized to combat the class of pathogen involved. 1 Effective T cell-mediated immunity against extracellular bacteria requires DCs to produce IL-1␤, IL-6, and IL-23 that contribute to the development of Th17 cells. 2,3 The pathogen-induced production of cytokines by DCs is induced on sensing of pathogens by pattern-recognition receptors (PRRs), including TLRs, C-type lectins, Nod-like receptors, and RIG-I-like receptors. [4][5][6][7] Although triggering of individual PRRs is known to induce cytokine production, it is becoming increasingly clear that the ultimate amount and the profile of cytokine production by DCs crucially depends on cross-talk between multiple PRRs. 8-10 However, our knowledge on these cross-talk mechanisms is likely to be still largely incomplete. 10 In this respect, the role of Fc␥Rs, the family of high-and low-affinity receptors for IgG, in the induction of cytokine production did not receive much attention. IgG is the most prevalent immunoglobulin in the blood and body tissues. 11,12 Because of the high levels of IgG directed against numerous polyreactive bacterial Ags, invading bacteria are efficiently opsonized as soon as they penetrate the body's barriers, even during primary infection. [13][14][15][16][17] IgG opsonization can directly lead to pathogen inactivation via complement activation, but can also result in a variety of responses by different effector immune cells such as cell degranulation, production of reactive oxygen species (ROS), or Ab-dependent cellular cytotoxicity (ADCC). 18,19 In addition, binding of opsonized pathogens to low-affinity Fc␥Rs on DCs mediates phagocytosis, degradation and subsequent presentation of pathogen-derived Ags to T cells. 20 Fc␥R stimulation also induces DC maturation. [21][22][23] However, the triggering of Fc␥Rs on DCs results in no or only low production of cytokines and has not been demonstrated to play a major role in polarization of human T-cell responses in healthy donors. 21,22 In the present study, we have taken into account that in most conditions DCs will engage bacteria that are IgG opsonized and that such DCs will be simultaneous triggered via Fc␥Rs and bacterial sensors. We here report that the engagement of DCs with opsonized bacteria resulted in strongly up-regulated production of selected cytokines, including IL-1␤ and IL-23, which favored the development of Th17 cells. This effect was fully dependent on stimulation of the low-affinity IgG receptor Fc␥RIIa (also known as CD32a), which synergized with TLRs for the amplification of Th17-promoting cytokines by both enhancing cytokine transcription and by activating caspase-1. Taken together, these data identified cross-talk between TLRs and Fc␥RIIa as a novel mechanism by which DCs promote the development of protective effector T cells in response to bacteria. ...

The mechanisms preventing detrimental T-cell responses against commensal skin bacteria remain elusive. Using monocyte-derived and skin-derived dendritic cells (DCs), we demonstrate that epidermal Langerhans cells (LCs), the DCs in the most superficial layer of the skin, have a poor capacity to internalize bacteria because of low expression of FcγRIIa. Furthermore, LCs show deficiency in processing and major histocompatibility complex II (MHC-II)-restricted presentation of bacterial antigens, as a result of a decreased expression of molecules involved in these functionalities. The reduced capacity to take up, process, and present bacterial antigens cannot be restored by LC activation by ectopically expressed Toll-like receptors or by cytokines. Consequently, bacteria-primed LCs poorly restimulate antibacterial memory CD4(+) T cells and inefficiently induce bacteria-specific effector CD4(+) T cells from naive T cells; however, they initiate the development of regulatory Foxp3(+)CD4(+) T cells, which are able to suppress the proliferation of autologous bystander T cells specific for the same bacteria. In contrast, dermal DCs that reside in the deeper dermal layer of the skin efficiently present bacterial antigens and provoke robust antibacterial naive and memory CD4(+) T-cell responses. In conclusion, LCs form a unique DC subset that is adapted at multiple levels for the maintenance of tolerance to bacterial skin flora.

Polymorphisms related to ORMDL3 are associated with asthma susceptibility, alterations in transcriptional regulation of ORMDL3, and changes in TH2 cytokine levels.

The objective of the current observational study was to determine the potential associations between cow factors, clinical mastitis (CM) etiology, and concentrations of select acute phase proteins and cytokines in milk from affected quarters of cows with CM. Cows with CM (n=197) were grouped based on systemic disease severity, milk culture result, parity, days in milk (DIM), previous CM occurrence, and season of the year when CM occurred. Concentrations of lipopolysaccharide-binding protein (LBP), haptoglobin (Hp), BSA, IFN-gamma, tumor necrosis factor-alpha (TNF-alpha), IL-1beta, IL-8, IL-10, IL-12, transforming growth factor (TGF)-alpha, and TGF-beta and activity of lactate dehydrogenase (LDH) were evaluated. Differences in the least squares means log(10) transformed concentrations of these proteins were compared using multiple linear regression mixed models. The milk concentrations of LBP, Hp, IL-1beta, IL-10, and IL-12, and activity of LDH in milk were higher in cows with moderate to severe versus mild systemic disease. The concentrations of Hp, BSA, IL-1beta, and IL-10 in milk were higher in cows with a gram-negative versus gram-positive milk culture result. Season of the year when CM occurred was associated with the concentration of all proteins evaluated except for IL-1beta and IL-12. Concentrations were higher in the winter versus summer except for Hp and TGF-beta, for which the opposite was true. Concentrations of LBP, IL-10, and IL-12, and LDH activity in milk were associated with DIM group. Except for LBP, these proteins were lower in cows with CM during the first 60 DIM versus those in mid or later lactation. Interferon-gamma, TNF-alpha, and IL-8 were undetectable in 67, 31, and 20% of samples, respectively. Detection of IFN-gamma and IL-8 was associated with season, and detection of TNF-alpha and IL-8 was associated with systemic disease severity. The current study provides the most comprehensive report of milk concentrations of innate immune response proteins in cows with naturally occurring CM and identifies factors that potentially influence those concentrations. Further investigation into the seasonal variation of cytokine production and its potential effect on the outcome of CM is warranted. Furthermore, the results of this study provide useful data for planning future studies examining the role of the innate immune response in CM.

IL-17-producing CD4 IntroductionIL-17 producing CD4 ϩ T helper (Th17) cells are important in immunity against extracellular pathogens, in particular at the mucosa, and are implicated in a variety of immune-mediated inflammatory disorders. Similar to other effector T cell types, Th17 cells develop from naive CD4 ϩ T cells in response to antigen presenting cell (APC)-derived signals. Whereas the cytokines IL-1␤, IL-6, IL-23, and TGF-␤ have been identified to support Th17 differentiation in both mice and human, there is less consensus on the costimulatory signals that drive the development of human Th17 cells. [1][2][3][4] A basic principle of T-cell activation is that proper stimulation of naive T cells requires costimulation via CD28 for survival and expansion, which licenses their subsequent development into distinct effector Th subsets driven by appropriate signal 3 factors. Surprisingly, 2 recent studies reported that Th17 development is selectively inhibited by CD28 costimulation. 5,6 One of these studies suggested that human Th17 development is alternatively mediated via ligation of the inducible costimulator (ICOS). 6 Among the other molecules that may alternatively costimulate CD4 ϩ T cells are the lymphocyte receptor CD5 and CD6. 7,8 CD5 and CD6 are both group B members of the Scavenger Receptor Cystein-Rich domains superfamily (SRCR-SF). CD5 and CD6 share important structural and functional properties, and have probably arisen from a common ancestral gene. During interaction between the APC and T cell, CD5 and CD6 form part of the immunologic synapse. 9,10 This localization makes them well positioned to modulate the signals that follow antigen-specific T-cell receptor (TCR) ligation. For CD5, this concept has been most clearly demonstrated. CD5 plays a role in the late events of synapse-mediated signal transduction, whereby the large cytoplasmatic domain of CD5 can recruit both positive and negative regulators of T-cell signaling. Consequently, CD5 is a modulator of T-cell responses with both stimulatory and inhibitory activities. 8,11 In the thymus, CD5 plays a role in regulating TCR-mediated expansion and survival during T-cell ontogeny. 7,8,12 In peripheral resting CD4 ϩ T cells, CD5 costimulation results in proliferation levels as high as obtained with classic CD28-mediated costimulation. A possible role of CD5-mediated costimulation of T cells in Th17 cell development is favored by the finding that mice deficient in signaling between CD5 and CK-2, a prosurvival serine/threonine kinase that associates with CD5, show diminished populations of IL-17-expressing T cells in the central nervous system, in a model of experimental autoimmune encephalomyelitis. 13 In the present study, we show that costimulation via CD5 or CD6 is superior to classic CD28 costimulation in driving Th17 cell development from human naive CD4 ϩ T cells. CD5 induces high and consistent levels of IL-17, indicating the induction of stable terminal differentiation. Indeed, CD5 promotes elevated expression of various intracellular fact...

S U M M A R Y During germinal center (GC) reactions, B-lymphocytes with high-affinity B-cell receptors are selected. Regulation of apoptosis is a key process in selecting such wanted B-cells and in eliminating B-cells with unwanted specificities. In this paper, we show that apoptosis in human GC B-cells involves lysosomal destabilization, which is strictly controlled by caspase-8 activity, but not by caspase-9 activity. Ligation of CD40 provides resistance to lysosomal destabilization. Experimental lysosomal rupture by the lysosomotropic drug O-methyl-L-serine dodecylamide hydrochloride (MSDH) induces apoptosis in GC B-cells, including phosphatidyl serine exposure, mitochondrial inactivation, and DNA fragmentation. These apoptotic features occur in the absence of caspase-3 activity. Follicular dendritic cells (FDCs) protect binding B-lymphocytes from lysosomal destabilization, in both the absence and the presence of MSDH. Our study demonstrates that lysosomal leakage induces apoptosis of GC B-cells in a caspase-3-independent manner and that high-affinity binding to FDCs prevents lysosomal leakage and apoptosis in GC B-cells.