Top down central nervous system (CNS) influences on the immune system and bottom up immune system influences on the CNS take part in a complex feedforward and feedback loop which may be responsible for initiating events and perpetuating circumstances in the course of neuropsychiatric as well as immune system diseases. In this paper the authors examine the neuroendocrine-neuroimmune stress response system, the concept of autoimmunoregulation, and recent studies of immune and pharmacological dysregulation in neuropsychiatric and psychosomatic illnesses. The authors review the recent English language literature on these subjects. Support for the hypothesis that macrophages play an important role in neurodevelopment and in the pathophysiology of various neuropsychiatric conditions is found. The interplay between neurologic and immune systems may help to uncover the pathophysiologies of certain neuropsychiatric systems. This may provide new strategies for pharmacologic anti inflammatory treatments. The monocyte /macrophage, which crosses the blood brain barrier is an essential candidate cell in the study of psychoneuroimmunology.