Different Asanas, Kriyas and pranayama remove toxins from body via sweat and gaseous exhange in lungs and cellular level. Organs & glands get stimulated, hormones are balanced and the nervous system gets relaxed. Other Pranayama methods, Mudras, Nadi Shuddhi Vyayama and Meditation also help in boosting immunity.
"Yoga for Everyone" Datta Kriya Yogo Vivardhatam!!