NO is a readily diffusible gas that has been established as a universal messenger, capable of mediating cell-cell communication throughout the body. Today, there is no simple, uniform picture of the function of NO in the immune system. Nitric oxide plays a pivotal role in cell-mediated immunity in neonates. During pregnancy NO act as immunomodulator. NO had a role between neuroendocrine and neuroimmune systems in physiological and pathological processes. It is involved in the pathogenesis and also the control of infectious diseases, autoimmunity, chronic degenerative diseases and tumours. So that protective and toxic effects of NO are frequently seen in parallel. Its striking inter and intracellular signaling capacity makes it extremely difficult to predict the effect of NOS inhibitors and NO donors, which still hampers therapeutic applications. This review will collate, contrast and compare recently published literature, to provide an up-to-date overview of the substantial role that NO plays within the neonate and pregnant animal immunity. 1303660646.php