LAUSR

Purpose: Immune populations and cytokines are known to exhibit distinct circadian ("daily") variations. We sought to characterize circadian-related immune variation in persons with type 1 diabetes (T1D) to ascertain whether sampling of peripheral immune biomarkers should be timed with circadian patterns Methods: We enrolled 10 adults (6 female) volunteers between 18 and 40 years of age, with T1D diagnosed for at least 12 months and free of other diseases. Subjects were admitted to the Research Center and had blood collections performed every 4 hours over a 24-hour period. Samples were processed and aliquoted after each draw. Flow cytometric analyses of central memory, regulatory, naive T- and B-cells, monocytes and NK cell frequencies were performed in 200μl. Circadian variation patterns were characterized with fitted cosine curves using COSINOR analysis. Results: Significant circadian patterns were identified for CD4 and CD8 T cells, T regulatory cells (T regs), Natural killer T cells (NKT), Dendritic Cells (DC) and B cells in T1D subjects. All populations except of NKT cells peaked during the night with peak levels estimated to occur respectively at (24:00 hour [95% CI]); CD4 0030 [2396,0040]; CD8 0106 [2358,0014]; T regs 2349 [2395,0005]; NKT 1527 [1217,1819]; DC 0070 [2392,0008]; B cells 0111 [2382,0014]. Conclusion: Clinical studies of immune interventions meant to influence immune populations should sample these populations at consistent times of day, and likely at peaks, or nadirs, in order to have the greatest range for therapeutic effect to be demonstrated. For B-cell reduction interventions (such as Rituximab), our study indicates the best time for PBMC sampling would be around midnight. For therapies targeting immune cell expansion, e.g., Treg expansion, the sampling may be better at nadir, where the increase will be the greatest- i.e., approximately noon. Disclosure E. Beli: None. L. DiMeglio: Research Support; Self; Amgen Inc., Caladrius Biosciences, Inc., Janssen Research & Development, Medtronic, Sanofi. Other Relationship; Self; Dexcom, Inc. S. Woerner: None. C. Evans-Molina: None. K.M. McGrail: None. C. Wasserfall: None. M.A. Atkinson: None. C. Beam: None. Funding JDRF International (3-SRA-2015-7-M-RJDRF, 3-APF-2017-396-A-N)