The aim of this review is not so much to show the problem of neuroendocrine, neurophysiologic, and neurochemical mechanisms of the immune system regulation of the organism by brain (there is a great deal of literature about it), as to solve the problem of whether the brain itself is an immune organ, and also to define cellular, neurochemical, and immunological properties of the brain for its immune defense when the blood-brain barrier is not damaged in spite of the penetration of the infection to brain. The accumulated literary data on CNS interaction with the immune system, expression of several cytokines and their receptors in the neurons of human brain culture, in astrocytes and microglia, all testify to the existence of a brain immune system. Recently studies appeared on the expression of major histocompatibility complex in brain neurons. It does not exclude the possibility of expression of immunoglobulins (or immunoglobulin-like proteins) in brain cells. Data obtained by us on the biosynthesis of a number of known interleukins and new cytokines in neurosecretory neurons of hypothalamus (N. Paraventricularis and N. Supraopticus) demonstrate that neuroendocrine nuclei of the hypothalamus are the center for neuroendocrine and immune systems of brain.