Social buffering of SIP effects. n = 20 adult macaques underwent a second 14-d SIP cycle paired with a juvenile macaque (solid lines/filled symbols). Effects were compared to isolated SIP trajectories (dashed lines/open symbols) for (A) major WBC subsets, (B) total monocytes, (C) dendritic cells, (D) plasma cortisol, (E) relative prevalence of classical versus nonclassical monocytes, (F) per-cell expression of Type I IFN response genes, and (G) RNA sequencing–based bioinformatic indications of IFN- related transcription factors (TFs: IRF, STAT, GFI) and neuroendocrine-related transcription factors (TFs) (GR, CREB). Values: mean ± SE; P values: SIP mode (isolated/paired) × SIP day interaction. *P < 0.05, **P < 0.01 difference from baseline.