Does yoga influence the immune system?

Yes, through the “inflammatory reflex”.  One physiological basis of the mind-body connection is the stimulation of the intestinal immune system by the vagus nerve – an effect first reported in 2000 by KJ Tracey and co-workers,  termed the ‘inflammatory reflex‘.

The vagus nerve is a key component of the Parasympathetic Nervous System (PNS); energizing the PNS enhances the activity of the vagus nerve.  Yoga, meditation, deep breathing, hypnosis and acupuncture have all been shown to enhance PNS activity, hence ‘vagal tone’ [see also citations in 2002 paper by Tracey above]    PNS activity can be easily measured by studying Heart Rate Variability (HRV), the variations in the time between successive beats of the heart.