Highlights  Alopecia areata is a polygenic and multifactorial autoimmune disease characterised by non-scarring hair loss.  Autoreactive CD8 + , CD4 + , natural killer cells and plasmacytoid dendritic cells infiltrate around the hair follicles during the growth (anagen) phase.  Increased cytokine activity, particularly IFN-γ, results in disruption of the hair follicle immune privilege and premature termination of the anagen phase, followed by hair follicle atrophy and dystrophy in persistent disease.

SummaryThe present study examines the temporal dynamics of macrophage activation marker expression in response to variations in stimulation. We demonstrate that markers can be categorized as 'early' (expressed most abundantly at 6 h post-stimulation) or 'late' (expressed at 24 h post-stimulation). Thus nos2 and p40 (IL-12/IL-23) are early markers of innate and classical activation, while dectin-1 and mrc-1 are early markers and fizz1 (found in inflammatory zone-1) and ym1 are late markers of alternative activation. Furthermore, argI is a late marker of both innate and alternative activation. The ability of interferon (IFN)-g to alter these activation markers was studied at both the protein level and gene level. As reported previously, IFN-g was able to drive macrophages towards the classical phenotype by enhancing nos2 gene expression and enzyme activity and p40 (IL-12/IL-23) gene expression in lipopolysaccharide (LPS)-stimulated macrophages. IFN-g antagonized alternative macrophage activation, as evident by reduced expression of dectin-1, mrc-1, fizz1 and ym1 mRNA transcripts. In addition, IFN-g antagonized arginase activity irrespective of whether macrophages were activated innately or alternatively. Our data explain some apparent contradictions in the literature, demonstrate temporal plasticity in macrophage activation states and define for the first time 'early' and 'late' markers associated with anti-microbial/inflammatory and wound healing responses, respectively.

T1/ST2 is an immunoregulatory protein of the IL-1 receptor family that has recently been reported as being a component of the IL-33 receptor. IL-33 is a newly described cytokine known to amplify the Th2 response and reduce production of Th1 cytokines. The function of T1/ST2 during Toxoplasma gondii infection is as yet undescribed. Given the requirement of a balanced type 1/type 2 response for effective control of parasite number and immunopathology, it is likely that T1/ST2 may play a part in aiding this process. Accordingly, we have shown that T1/ST2 mRNA transcripts are upregulated in the brains of mice infected with T. gondii and that mice deficient in T1/ST2 demonstrated increased susceptibility to infection with T. gondii that correlated with increased pathology and greater parasite burden in the brains. Real-time PCR analysis of cerebral cytokine levels revealed increased mRNA levels of iNOS, IFN-c and TNF-a in infected T1/ST2 À/À mice. These effects were independent of changes in IL-10 production. This study provides the first evidence of a specific role for IL-33 receptor signalling in the brain as well as highlighting the requirement of this mechanism in limiting infection with an intracellular parasite.Key words: Encephalitis . IL-33 . IL-33 receptor . Th1/Th2 . Toxoplasma IntroductionThe receptor T1/ST2 is a member of the IL-1 receptor family that also includes the TLR and the IL-18R [1]. Further characterisation revealed that differential splicing of T1/ST2 mRNA led to production of two different transcripts encoding either a transmembrane form (ST2L) or a soluble, secreted form (sST2) [2]. T1/ST2 is expressed by a number of haematopoetic cells such as T cells, mast cells, macrophages, NK cells and invariant NKT cells [3][4][5][6][7]. ST2L has previously been used as a marker for Th2 cells although T1/ST2-negative Th2 cells exist with reports that ST2L may be better described as a marker of effector Th2 cells enhancing the Th2 response rather than aiding its development [3,[8][9][10]. As well as promoting a Th2 response ST2L has been shown to sequester the signalling molecules MyD88 and Mal to inhibit subsequent cytokine production following TLR ligation [10]. sST2 also plays a role in downregulating the inflammatory response [6,11]. 426T1/ST2 is the ligand-binding component of the receptor for the cytokine IL-33 which, together with the IL-1 receptor accessory protein, forms the IL-33 receptor [12,13]. IL-33 is a member of the IL-1 family with the ability to downregulate IFN-g production by Th1 cells in vitro and upregulate the production of the Th2 cytokines IL-5 and IL-13 from Th2 cells both in vitro and in vivo [12]. Therefore, the function of IL-33 reinforces the previously described role of T1/ST2 in enhancing a Th2 response while reducing a Th1 response.Protective immunity to the protozoan parasite Toxoplasma gondii relies on a delicate balance of type 1/type 2 immune responses to effectively control parasite proliferation and prevent pathology caused by an over-exuberant type-1 response [14]...

The structure and location of Toxoplasma gondii apicoplasts were examined in intermediate and definitive hosts and shown to vary in a stage-specific manner. Immunocytochemistry and electron microscopy studies were used to identify changes in the morphology of apicoplasts and in their enoyl reductase (ENR) content during asexual and sexual development. Apicoplasts in tachyzoites were small, multimembraned organelles anterior to nuclei that divided and segregated with the nuclei during endodyogeny. In nonproliferating bradyzoites within mature tissue cysts (1 to 24 months), apicoplasts had high levels of ENR. During coccidian development, asexual multiplication (endopolygeny), resulting in simultaneous formation of up to 30 daughters (merozoites), involved an initial growth phase associated with repeated nuclear divisions during which apicoplasts appeared as single, elongated, branched structures with increased levels of ENR. At initiation of merozoite formation, enlarged apicoplasts divided simultaneously, with constrictions, into portions that segregated to developing daughters. In sexual stages, apicoplast division did not occur during microgametogony, and apicoplasts were absent from the microgametes that were formed. In contrast, during macrogametogony, the apicoplast appeared as a large, branched, perinuclear structure that had very high levels of ENR in the absence of nuclear division. Marked increases in the size of apicoplasts and levels of ENR may be related to requirements of the macrogametocytes to synthesize and store all components necessary for oocyst formation and subsequent extracellular sporulation. Thus, it is shown that apicoplasts are present and contain ENR in all T. gondii life cycle stages except microgametes, which will result in maternal inheritance of the organelle.

Summary Macrophage function has been demonstrated to be subject to modulation by progesterone. However, as this steroid hormone can act through the glucocorticoid receptor as well as the progesterone receptor, the mechanism of action has not been precisely characterized. To determine the mode of action, we compared the ability of progesterone, norgestrel (a synthetic progesterone‐receptor‐specific agonist) and dexamethasone (a synthetic glucocorticoid receptor agonist) to modulate macrophage function following stimulation of the Toll‐like receptor‐4 (TLR‐4) ligand lipopolysaccharide (LPS). The results demonstrate that following stimulation of TLR‐4 with LPS and cotreatment with either progesterone or dexamethasone, but not norgestrel, there is a significant reduction in nitric oxide (NO) production, indicating that this progesterone‐mediated effect is through ligation of the glucocorticoid receptor. In contrast, LPS‐induced interleukin‐12 (IL‐12) production could be downregulated by all three steroids, indicating that ligation by progesterone of either the glucocorticoid or the progesterone receptors or both could mediate this effect. While progesterone downmodulated NO‐mediated killing of Leishmania donovani by activated macrophages in vitro, most probably via the glucocorticoid receptor, it had little effect on Toxoplasma gondii growth in these cells. This would suggest that progesterone‐mediated increased susceptibility to T. gondii during pregnancy is more likely to be related to the ability of the hormone to downregulate IL‐12 production and a type‐1 response utilizing the progesterone as well as the glucocorticoid receptors.