Here we identified a population of bone marrow neutrophils that constitutively express RORγt and which can produce and respond to IL-17A (IL-17). IL-6, IL-23 and RORγt, but not T cells or NK cells, are required for IL-17 production in neutrophils. IL-6 and IL-23 induced IL-17RC and Dectin-2 expression in neutrophils, and expression of IL-17RC was augmented by Aspergillus and Dectin-2 activation. Autocrine IL-17A–IL-17 receptor activity induced production of reactive oxygen species (ROS), and increased fungal killing in vitro and in a model of Aspergillus keratitis. Human neutrophils also expressed RORγt, and induced IL-17A, IL-17RC and Dectin-2 expression following IL-6 and IL-23 stimulation. These findings identify a population of human and murine neutrophils that exhibit autocrine IL-17 activity, and which likely contribute to the etiology of microbial and inflammatory diseases.

The adaptive immune system functions through the combined action of antigen-presenting cells (APCs) and T cells. Specifically, class I major histocompatibility complex antigen presentation to CD8(+) T cells is limited to proteosome-generated peptides from intracellular pathogens while the class II (MHCII) endocytic pathway presents only proteolytic peptides from extracellular pathogens to CD4(+) T cells. Carbohydrates have been thought to stimulate immune responses independently of T cells; however, zwitterionic polysaccharides (ZPSs) from the capsules of some bacteria can activate CD4(+) T cells. Here we show that ZPSs are processed to low molecular weight carbohydrates by a nitric oxide-mediated mechanism and presented to T cells through the MHCII endocytic pathway. Furthermore, these carbohydrates bind to MHCII inside APCs for presentation to T cells. Our observations begin to elucidate the mechanisms by which some carbohydrates induce important immunologic responses through T cell activation, suggesting a fundamental shift in the MHCII presentation paradigm.

Commensalism is critical to a healthy Th1/Th2 cell balance. Polysaccharide A (PSA), which is produced by the intestinal commensal Bacteroides fragilis, activates CD4+ T cells, resulting in a Th1 response correcting the Th2 cell skew of germ-free mice. We identify Toll-like receptors as crucial to the convergence of innate and adaptive responses stimulated by PSA. Optimization of the Th1 cytokine interferon-γ in PSA-stimulated dendritic cell–CD4+ T cell co-cultures depends on both Toll-like receptor (TLR) 2 and antigen presentation. Synergy between the innate and adaptive responses was also shown when TLR2−/− mice exhibited impaired intraabdominal abscess formation in response to B. fragilis. Commensal bacteria, using molecules like PSA, potentially modulate the Th1/Th2 cell balance and the response to infection by coordinating both the innate and adaptive pathways.

Unlike their protein “roommates” and their nucleic acid “cousins,” carbohydrates remain an enigmatic arm of biology. The central reason for the difficulty in fully understanding how carbohydrate structure and biological function are tied is the nontemplate nature of their synthesis and the resulting heterogeneity. The goal of this collection of expert reviews is to highlight what is known about how carbohydrates and their binding partners—the microbial (non-self), tumor (altered-self), and host (self)—cooperate within the immune system, while also identifying areas of opportunity to those willing to take up the challenge of understanding more about how carbohydrates influence immune responses. In the end, these reviews will serve as specific examples of how carbohydrates are as integral to biology as are proteins, nucleic acids, and lipids. Here, we attempt to summarize general concepts on glycans and glycan-binding proteins (mainly C-type lectins, siglecs, and galectins) and their contributions to the biology of immune responses in physiologic and pathologic settings.

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Full-length Drosophila kinesin heavy chain from position 1 to 975 was expressed in Escherichia coil (DKH975) and is a dimer. The sedimentation coefficient of DKH975 shifts from 5.4 S at 1 M NaCl to ϳ6.9 S at <0.2 M NaCl. This transition of DKH975 between extended and compact conformations is essentially identical to that for the heavy chain dimer of bovine kinesin (Hackney, D. D., Levitt, J. D., and Suhan, J. (1992) J. Biol. Chem. 267, 8696 -8701). Thus the capacity for undergoing the 7 S/5 S transition is an intrinsic property of the heavy chains and requires neither light chains nor eukaryotic post-translational modification. DKH960 undergoes a similar transition, indicating that the extreme COOH-terminal region is not required. More extensive deletions from the COOH-terminal (DKH945 and DKH937) result in a shift in the midpoint for the transition to lower salt concentrations. DKH927 and shorter constructs remaining extended even in the absence of added salt. Thus the COOH-terminal ϳ50 amino acids are required for the formation of the compact conformation. Separately expressed COOH-terminal tail segments and NH 2 -terminal head/neck segments interact in a salt-dependent manner that is consistent with the compact conformer being produced by the interaction of domains from these regions of the heavy chain dimer. The microtubule-stimulated ATPase rate of DKH975 in the compact conformer is strongly inhibited compared with the rate of extended DKH894 (4 s ؊1 and 35 s ؊1 , respectively, for k cat at saturating microtubules).Kinesin is an ATP-dependent motor protein that is involved in movement of membranous vesicles along MTs 1 (see Refs. 1 and 2). The NH 2 -terminal ϳ340 amino acids of the heavy chain forms a globular motor domain (head) that has MT-stimulated ATPase activity (see Fig. 2B). The motor domain is followed by a long central coiled-coil stalk region and a small nonhelical domain at the COOH-terminal. The central region contains several positions at which the coiled-coil propensity is low and these likely represent hinges in the stalk. The first coiled-coil region that extends from the motor domain is designated the neck region. Constructs that contain the head and the COOHterminal part of the coiled-coil neck form dimers (3). There is a likely hinge at position ϳ400 that marks the boundary between the neck and the stalk. Peptides from the neck (4, 5) and stalk (6) have been demonstrated to interact in a coiled-coil manner by several criteria. The crystal structure of a dimeric head plus neck construct has been recently determined (7) and it directly demonstrates the coiled-coil interactions in the neck region.Native kinesin is a heterotetramer composed of a dimeric heavy chain core with two light chains attached in the COOHterminal region (8, 9). At high salt kinesin exist in an extended conformation with an s 20,w value of ϳ6 S, but adopts a more compact conformation at low salt concentration with an s 20,w value of ϳ9 S. This global conformational transition is readily reversible and can be observed b...

␣-Crystallin, a large lenticular protein complex made up of two related subunits (␣A-and ␣B-crystallin), is known to associate increasingly with fiber cell plasma membranes with age and/or the onset of cataract. To understand better the binding mechanism, we developed a sensitive membrane binding assay using lens plasma membranes and recombinant human ␣A-and ␣B-crystallins conjugated to a small fluorescent tag (Alexa350 ® ). Both ␣A and ␣B homopolymer complexes, as well as a reconstituted 3:1 heteromeric complex, bind to lens membranes in a specific, saturable, and partially irreversible manner that is sensitive to both time and temperature. The amount of ␣-crystallin that binds to the membrane increases under acidic pH conditions and upon removal of exposed intrinsic membrane protein domains but is not affected at high ionic strength, suggesting that ␣-crystallin binds to the fiber cell plasma membranes mainly through hydrophobic interactions. The binding capacity and affinity for the reconstituted 3:1 heteromeric complex were measured to be 3.45 ؎ 0.11 ng/g of membrane and 4.57 ؎ 0.50 ؋ 10 ؊4 g ؊1 of membrane, respectively. The present membrane binding data support the hypothesis that the physical properties of a mixed ␣-crystallin complex may hold particular relevance for the function of ␣-crystallin within the lens.

IgG carrying terminal α2,6-linked sialic acids added to conserved N-glycans within the Fc domain by the sialyltransferase ST6Gal1 accounts for the anti-inflammatory effects of large-dose i.v. Ig (IVIg) in autoimmunity. Here, B-cell-specific ablation of ST6Gal1 in mice revealed that IgG sialylation can occur in the extracellular environment of the bloodstream independently of the B-cell secretory pathway. We also discovered that secreted ST6Gal1 is produced by cells lining central veins in the liver and that IgG sialylation is powered by serum-localized nucleotide sugar donor CMP-sialic acid that is at least partially derived from degranulating platelets. Thus, antibody-secreting cells do not exclusively control the sialylationdependent anti-inflammatory function of IgG. Rather, IgG sialylation can be regulated by the liver and platelets through the corresponding release of enzyme and sugar donor into the cardiovascular circulation.W hile en route to the plasma membrane as integral membrane proteins or for secretion, glycoproteins exiting the endoplasmic reticulum traverse the cis-, medial-, and trans-Golgi apparatus where the associated N-linked glycans are remodeled into their final form. This classically defined secretory pathway dictates that the glycoform of all glycoproteins produced by a cell is largely determined by the cohort of enzymes within the Golgi and the metabolic circumstances of that specific cell.Protein glycosylation is known to play fundamental roles in all aspects of biology, but has recently gained significant attention in immunology. When administered at high doses, i.v. Ig (IVIg) is an effective anti-inflammatory treatment for autoimmune patients (1). In 2006, it was discovered that the ∼10% of IgG molecules that carry α2,6-linked sialic acids upon the conserved biantennary N-glycans within the Fc domain provided the potent IVIg anti-inflammatory activity in autoimmune disease (2). Indeed, enrichment for the sialylated IgG (sIgG) fraction from IVIg pools increased the efficacy of treatment in mouse models of arthritis 100-fold in an IL-4-dependent fashion through receptors such as CD209 (DC-SIGN) (3, 4). Moreover, it was reported that sialylation of IgG also impacts antibody affinity maturation, although the mechanism underlying this phenomenon remains to be fully elucidated (5). These data indicate that sialylation serves as the mechanism underlying pleotropic IgG function (3,4,6).Epidemiologic analyses published since the reports cited above are consistent with this model. For example, female rheumatoid arthritis patients often go into remission during pregnancy and then relapse following childbirth. Analysis of sIgG levels before, during, and after pregnancy showed that the level of sIgG increases rapidly during pregnancy-induced remission, whereas during periods of exacerbated disease, sIgG is essentially undetectable (7,8). To date, it is unclear whether IgG sialylation patterns precede or result from the inflammatory state, and essentially nothing is known about the regulatory mecha...