In response to infections and irritants, the respiratory epithelium releases the alarmin interleukin (IL)-33 to elicit a rapid immune response. However, little is known about the regulation of IL-33 following its release. Here we report that the biological activity of IL-33 at its receptor ST2 is rapidly terminated in the extracellular environment by the formation of two disulphide bridges, resulting in an extensive conformational change that disrupts the ST2 binding site. Both reduced (active) and disulphide bonded (inactive) forms of IL-33 can be detected in lung lavage samples from mice challenged with Alternaria extract and in sputum from patients with moderate–severe asthma. We propose that this mechanism for the rapid inactivation of secreted IL-33 constitutes a ‘molecular clock' that limits the range and duration of ST2-dependent immunological responses to airway stimuli. Other IL-1 family members are also susceptible to cysteine oxidation changes that could regulate their activity and systemic exposure through a similar mechanism.

The pathogenesis of infection with Yersinia pestis, the causative agent of plague, was examined following subcutaneous infection of BALB/c mice with a fully virulent strain expressing green fluorescent protein. Plate culturing, flow cytometry, and laser confocal microscopy of spleen homogenates throughout infection revealed three discernible stages of infection. The early phase was characterized by the presence of a small number of intracellular bacteria mostly within CD11b؉ macrophages and Ly-6G ؉ neutrophils. These bacteria were not viable, as determined by plate culturing of spleen homogenates, until day 2 postinfection. Between days 2 and 4 postinfection, a plateau phase was observed, with bacterial burdens of 10 3 to 10 4 CFU per spleen. Flow cytometric analysis revealed that there was even distribution of Y. pestis within both CD11b؉ macrophage and Ly-6G ؉ neutrophil populations on day 2 postinfection. However, from day 3 postinfection onward, intracellular bacteria were observed exclusively within splenic CD11b ؉ macrophages. The late phase of infection, between days 4 and 5 postinfection, was characterized by a rapid increase in bacterial numbers, as well as escape of bacteria into the extracellular compartment. Annexin V staining of spleens indicated that a large proportion of splenic neutrophils underwent rapid apoptosis on days 1 and 2 postinfection. Fewer macrophages underwent apoptosis during the same period. Our data suggest that during the early stages of Y. pestis infection, splenic neutrophils are responsible for limiting the growth of Y. pestis and that splenic macrophages provide safe intracellular shelters within which Y. pestis is able to grow and escape during the later stages of infection. This macrophage compliance can be overcome in vitro by stimulation with a combination of gamma interferon and tumor necrosis factor alpha.

This paper is an attempt to apply the methods of the theory of algebras to the more general problem of the structure of semi-groups, i.e. systems with one composition, satisfying the associative law.

No abstract

Interleukin (IL)-13 is a pleiotropic T helper type 2 cytokine frequently associated with asthma and atopic dermatitis. IL-13-mediated signalling is initiated by binding to IL-13Rα1, which then recruits IL-4Rα to form a heterodimeric receptor complex. IL-13 also binds to IL-13Rα2, considered as either a decoy or a key mediator of fibrosis. IL-13-neutralising antibodies act by preventing IL-13 binding to IL-13Rα1, IL-4Rα and/or IL-13Rα2. Tralokinumab (CAT-354) is an IL-13-neutralising human IgG4 monoclonal antibody that has shown clinical benefit in patients with asthma. To decipher how tralokinumab inhibits the effects of IL-13, we determined the structure of tralokinumab Fab in complex with human IL-13 to 2 Å resolution. The structure analysis reveals that tralokinumab prevents IL-13 from binding to both IL-13Rα1 and IL-13Rα2. This is supported by biochemical ligand-receptor interaction assay data. The tralokinumab epitope is mainly composed of residues in helices D and A of IL-13. It is mostly light chain complementarity-determining regions that are driving paratope interactions; the variable light complementarity-determining region 2 plays a key role by providing residue contacts for a network of hydrogen bonds and a salt bridge in the core of binding. The key residues within the paratope contributing to binding were identified as Asp50, Asp51, Ser30 and Lys31. This study demonstrates that tralokinumab prevents the IL-13 pharmacodynamic effect by binding to IL-13 helices A and D, thus preventing IL-13 from interacting with IL-13Rα1 and IL-13Rα2.

The critical role played by IgE in allergic asthma is well-documented and clinically precedented, but some patients in whom IgE neutralization may still offer clinical benefit are excluded from treatment with the existing anti-IgE therapy, omalizumab, due to high total IgE levels or body mass. In this study, we sought to generate a novel high affinity anti-IgE antibody (MEDI4212) with potential to treat a broad severe asthma patient population. Analysis of body mass, total and allergen-specific IgE levels in a cohort of severe asthmatics was used to support the rationale for development of a high affinity IgE-targeted antibody therapeutic. Phage display technology was used to generate a human IgG1 lead antibody, MEDI4212, which was characterized in vitro using binding, signaling and functional assay systems. Protein crystallography was used to determine the details of the interaction between MEDI4212 and IgE. MEDI4212 bound human IgE with an affinity of 1.95 pM and was shown to target critical residues in the IgE Cε3 domain critical for interaction with FcεRI. MEDI4212 potently inhibited responses through FcεRI and also prevented the binding of IgE to CD23. When used ex vivo at identical concentration, MEDI4212 depleted free-IgE from human sera to levels ~1 log lower than omalizumab. Our results thus indicate that MEDI4212 is a novel, high affinity antibody that binds specifically to IgE and prevents IgE binding to its receptors. MEDI4212 effectively depleted free-IgE from human sera ex vivo to a level (1 IU/mL) anticipated to provide optimal IgE suppression in severe asthma patients.

In this note we are concerned with the semi-group 8 nr , generated by n of its elements, in which each element x satisfies the equation x r = x, the semi-group being otherwise free. The main result proved is that the proposition (A,) S nr is finite for all finite n, is equivalent to the proposition (B r ) the group B nr _ x , generated by n of its elements, in which each element x satisfies the equation x r~x = 1, the group being otherwise free, is finite for all finite n. The latter proposition (Burnside's conjecture for r-1) is known to be true for r = 2,3,4. Hence the above result shows that 8 nr is certainly finite if r = 2,3, 4. In the case r = 2, the methods of this paper enable us to give a formula for the number of elements in 8 nr .Denote the generators of 8 nr by a v a 2 ,...,a n . Then, following customary procedure, we consider the set of 'words' or finite sequences (including the empty sequence) composed of the letters a v a 2 , ...,a n . Such words will be denoted by capital letters A, B, W, ..., while the symbols AB, A k will have their usual meanings of A followed by B', and 'A repeated k times'.We may now consider the elements of S nr as being classes of equivalent non-empty words, two words W and W being equivalent (TF~ W) if W can be transformed into W by a finite sequence of 'moves', each move being a transformation of one of the following two types:(a) replace a word AXB by AX r B, (6) replace a word AX r B by AXB.If W is a word, denote by S( W) the set of letters which appear in W at least once. Then, clearly, moves of type (a) and (b), applied to W, leave S(W) invariant. Hence(1) If W~ W, then 8{W) = 8(W). Further, we have, almost immediately,(2) S(WW) = 8(W)u S(W'), for any two words W, W. Let S be a non-empty subset of the set {a v a 2 ,...,a n }. Denote by C s the set of all elements of 8 nr which have a representative W such that S( W) = 8. Then clearly S nr is the union of the sets C s , where 8 varies over the non-empty subsets of {a v ...,a n }, while by (1) above, these sets are disjoint, and by (2) are themselves semi-groups. If 8 = {ax,. .-,«"}, we shall write G nr for C s . Then, if S contains k elements, it is clear that C s is isomorphic to C kr . From this follows immediately LEMMA 1. Let s nr denote the number of elements in S nr , and c nr the number of elements in C nr . Then n 3-2

Summary.Previous work has shown that the type strain of Streptococcus sanguis, NCTC 7863, induces aggregation of normal platelets by a complement-dependent mechanism. We investigated the roles of IgG and fibrinogen in the aggregation process. Plasma depleted of IgG by passage through protein A-sepharose failed to support platelet aggregation, as did plasma absorbed at 0ЊC with whole bacteria. However, absorption of plasma with a non-aggregating strain of S. sanguis, SK96, did not remove aggregating activity for NCTC 7863. Supplementing 0ЊC-absorbed plasma with purified IgG restored the aggregation supporting activity. A monoclonal antibody to the FcgRII receptor inhibited platelet aggregation by the bacteria, indicating a requirement for bacteria-IgG complexes interacting with the Fc receptor in platelet aggregation. There was a lag time to the onset of platelet aggregation of 7-19 min depending upon the platelet donor, but the length of this lag did not correlate with either total IgG concentration recognizing NCTC 7863 in subjects' plasma, or the concentration any of the four IgG subclasses or with IgG avidity levels.Fibrinogen was shown to bind rapidly to the bacterial cell surface. Monclonal antibody to GPIIb/IIIa, RGDS peptide, and a specific antagonist for the platelet fibrinogen receptor, GPIIb/IIIa, FK633, inhibited platelet aggregation by NCTC 7863, indicating that platelet aggregation is fibrinogen dependent. These data suggest that platelet aggregation by some strains of S. sanguis requires multiple stimuli/agonists, including IgG-Fc receptor interaction, complement and fibrinogen.