Synchronization of the Normal Human Peripheral Immune System: A Comprehensive Circadian Systems Immunology Analysis

Abstract

In this study, we sought to fill an important gap in fundamental immunology research by conducting a comprehensive systems immunology analysis of daily variation in the normal human peripheral immune system. Although variation due to circadian rhythmicity was not a significant source of variation in daily B-cell levels or any CD4+ functional subset, it accounted for more than 25% of CD4+ regulatory T-cell variation and over 50% of CD8+ central memory variation. circadian rhythmicity demonstrated phase alignment within functional phenotypes. In addition, we observed that previouslydescribed mechanistic relationships can also appear in the peripheral system as phase shifting in rhythmic patterns. We identified a set of immune factors which are ubiquitously correlated with other factors and further analysis also identified a tightly-correlated "core" set whose relational structure persisted after analytically removing circadian-related variation. This core set consisted of CD8+ and its subpopulations and the NK population. In sum, the peripheral immune system can be conceptualized as a dynamic, interconnected wave-field repeating its pattern on a daily basis. Our data provide a comprehensive inventory of synchronization and correlation within this wave-field and we encourage use of our data to discover unknown mechanistic relationships which can then be tested in the laboratory.Immune variation, in both circulating cell frequency and phenotype, have been associated with multiple autoimmune diseases 1 . For example, variations in subsets of immune cells have been correlated to metabolic changes in type 1 diabetes 2,3 and found predictive of disease progression in multiple sclerosis 4 . Additionally, peripheral blood immune cell variations were demonstrated to be predictive of a post-vaccination response 5 . Over the long-term, variation within an individual appears to be relatively stable compared to variation between-individuals 6 .Shorter-term variation occurring within the course of a day (i.e., circadian) is now a well-established characteristic of human immunity in circulation 7-15 . The presence of a "master clock", entraining the organism to external light cues via the suprachiasmic nuclei of the neuroendocrine system, is thought to be a major but not exclusive driver of the circadian behavior seen in certain components of the human immune system. Circadian changes in immune cell function and abundance within the circulatory system are also thought to result from transcriptional and posttranslational feedback loops generated by a set of interplaying clock proteins and time-keeping clock genes 16 . These "peripheral clocks" and their transcription/translation are now believed to function in nearly every human cell 17 . Immune factors such as cytokines can also influence the circadian clock, providing bidirectional flow of circadian information between the neuroendocrine and immune system 18 . Mavroudis 18 hypothesized that this network of neuroendocrine-immune interactions consist of complex and integrated mole...

Nonclassical Monocytes (CD14dimCD16+) Are Associated With Carotid Intima-Media Thickness Progression for Men but Not Women

“… 38 An additional limitation relates to variable timing of blood draws for PBMC processing, which generally occurred in the mornings but not at the same time for each individual (eg, 8 am versus 11 am ). Given emerging data indicating intraindividual circadian variations in circulating immune cell subsets, 39 there is potential unmeasured confounding related to the timing of blood draws. However, due to the largely random nature of blood draw timing unrelated to participant characteristics and IMT risk factors, if confounding is present, it would most likely bias toward the null via regression-dilution rather than toward false-positive.…”

Peripheral immune circadian variation, synchronisation and possible dysrhythmia in established type 1 diabetes

“…Blood samples were aliquoted, with one sample processed immediately at each collection time at the IU Research Center ('fresh') and the other shipped (ambient) to University of Florida (UF) ('shipped') for processing. The shipped samples were analysed at UF in order to compare the participants with type 1 diabetes against HC samples that had been collected earlier and which had also been shipped (ambient) to UF (HC data reported by Beam et al [28]). Both the type 1 diabetes and HC samples were processed under the same protocol using the same cytometer and by the same UF personnel.…”

“…Cytokines Plasma was isolated from EDTA tubes by centrifugation with the remaining sample after flow cytometry aliquots were dispensed. This was then immediately frozen until batch analyses using Luminex (Austin, TX, USA) technology and kits from Millipore (Burlington, MA, USA) as previously described [28].…”

“…I n a d d i t i o n , w e a d j u s t e d f o r i n d i v i d u a l participant-level differences in the dynamic range of immune factors via standardisation prior to analysis and adjusted for individual variation in the timing of individual participant-level circadian rhythms by incorporating the simultaneous measurement of cortisol in our statistical models. Statistical methods for systems immunology analysis of the data follow those used previously by the team [28]. Further details can be found in the ESM Methods.…”

Peripheral neuroimmune interactions: selected review and some clinical implications

“…Norepinephrine is essential for antigen processing and trafficking of activated lymphocytes into circulation [ 69 , 70 ]. Several lymphocyte subtypes express cell-intrinsic circadian clocks [ 71 ], which may contribute to rhythmicity to lymphocyte migration [ 72 ].…”