The immune system is a key component in 'psychosomatic' disorders which usually have an auto-immune aspect. The immune system is a much slower system than both the voluntary muscular system, and the autonomic nervous system. It responds over days and weeks. Because of this, in our 'instant' culture, it is little trusted or relied upon bexcept when it 'goes wrong'
Though it is litle understood how exactly it occurs, the immune system seem to communicateswith the brain via the afferent fibers of the vagus in the viscera.
What is relevant in the Reich and Lowen tradition about the immune system is not how it acts toward foreign bodies and micro-organisms, but how it acts towards one's own body. Stress plays havoc with the 'economy' of cortisol, which is an important regulator of immune response. In interpersonal matters, immune responses, including allergies and auto-immune disorders might be thought of as last-ditch efforts to address a problem (threat to integrity) that the voluntary and autonomic systems have failed to solve. No one really seems to understand the immune system or the mechanism of autoimmune disorders. Allopathic medicine treats auto-immune disorders with more cortisol-like drugs, or increasingly with potent immunalsuppressants, which may provide symptomatic relief, but are not re-regulating, but further dysregulating.