Circadian rhythms in immunity and host-parasite interactions.

The mammalian immune system adheres to a 24 h circadian schedule, exhibiting daily rhythmic patterns in homeostatic immune processes, such as immune cell trafficking, as well as the inflammatory response to infection. These diurnal rhythms are driven by endogenous molecular clocks within immune cells which are hierarchically coordinated by a light-entrained central clock in the suprachiasmatic nucleus of the hypothalamus and responsive to local rhythmic cues including temperature, hormones and feeding time. Circadian control of immunity may enable animals to anticipate daily pathogenic threat from parasites and gate the magnitude of the immune response, potentially enhancing fitness. However, parasites also strive for optimum fitness and some may have co-evolved to benefit from host circadian timing mechanisms, possibly via the parasites' own intrinsic molecular clocks. In this review, we summarize the current knowledge surrounding the influence of the circadian clock on the mammalian immune system and the host-parasitic interaction. We also discuss the potential for chronotherapeutic strategies in the treatment of parasitic diseases.

Chronotype in Patients With Immune-Mediated Inflammatory Disease: A Systematic Review.

Immune-mediated inflammatory diseases (IMIDs) such as rheumatoid arthritis, inflammatory bowel disease, and asthma share common pathophysiological pathways characterized by chronic inflammation and subsequent tissue damage involving multiple body sites. Circadian rhythms are 24-h body cycles that regulate immune activity and control the magnitude of immune response based on time of day. Chronotype is a person's individual circadian phase preference, ranging from morningness to eveningness, which is known to influence the risk of cardiometabolic and mental health disease. We systematically reviewed the literature to assess the association of questionnaire-based chronotype and patients with IMID. A comprehensive search of MEDLINE and Embase identified 12 studies meeting the inclusion criteria, conducted in 7 countries and covering 4 IMIDs to include 15,625 IMID patients and 410,783 healthy controls. Results showed that later chronotype may be a risk factor for worse quality of life and increased symptom burden in patients with IMIDs. In addition, chronotype may be a risk factor for IMID incidence, but the direction and magnitude of this effect were not consistent across individual IMIDs. Chronotype assessment could contribute to risk stratification in patients with IMIDs. Cross-disciplinary collaboration to understand the role of circadian rhythms and chronotype in driving common inflammatory pathways could help to improve outcomes for patients with IMIDs.

Circadian Host-Microbiome Interactions in Immunity.

The gut microbiome plays a critical role in regulating host immunity and can no longer be regarded as a bystander in human health and disease. In recent years, circadian (24 h) oscillations have been identified in the composition of the microbiota, its biophysical localization within the intestinal tract and its metabolic outputs. The gut microbiome and its key metabolic outputs, such as short chain fatty acids and tryptophan metabolites contribute to maintenance of intestinal immunity by promoting barrier function, regulating the host mucosal immune system and maintaining the function of gut-associated immune cell populations. Loss of rhythmic host-microbiome interactions disrupts host immunity and increases risk of inflammation and metabolic complications. Here we review factors that drive circadian variation in the microbiome, including meal timing, dietary composition and host circadian clocks. We also consider how host-microbiome interactions impact the core molecular clock and its rhythmic outputs in addition to the potential impact of this relationship on circadian control of immunity.

Trends in dermoscopy use in the UK: results from surveys in 2003 and 2012.

BACKGROUND: Dermoscopy is a useful tool to aid diagnosis of pigmented and non-pigmented skin lesions, as well as many other dermatological conditions. Use of dermoscopy is increasing worldwide, but to date, there are no reported data on attitudes of dermatologists in the United Kingdom (UK) towards dermoscopy. OBJECTIVE: To determine current attitudes of UK dermatologists towards dermoscopy and assess how these attitudes have changed over the last decade. METHODS: In October 2012, an online survey was sent to members of British Association of Dermatologists over a 12-week period. Data were subsequently compared with data from a similar UK nationwide paper questionnaire distributed to members in 2003. RESULTS: The 2003 survey collected 292 responses (uptake 42%), and in 2012 there were 209 responses (22%), predominantly from consultants and registrars. In 2012, 86% respondents reported increased use of dermoscopy over the previous decade with 98.5% of respondents reporting regular clinical use of dermoscopy, compared with 54% in 2003. Overall, 81% respondents in 2012 had received dermoscopy training, mainly from UK-based courses (62% of respondents) but increasingly via Internet-based resources (30% vs. 7% in 2003). However, 39% respondents lacked confidence when making a diagnosis based on their interpretation of dermoscopy findings. CONCLUSIONS: Over the last decade, use of dermoscopy has increased amongst UK dermatologists and the majority of respondents now employ dermoscopy in daily clinical practice. However, the use of dermoscopy in the dermatology community overall is not known and for those individuals there is a continued need for education.