One of the most effective plants for with acute or chronic rejection ladder is uva ursi (Arctostaphylos uva-ursi). The name means "grapes of the bear" and refers to its unpleasant-tasting grape-like fruit. No one but a bear would want to eat it!
Uva ursi has been used since the earliest days of herbal medicine -- 13th century records show that it was used in Britain by the famous holistic Welsh physicians of Myddfai.