There seems little doubt that extensive communications between the immune systems and the central nervous system do exist. Besides direct contacts between the cells of the two compartments, soluble factors are clearly involved. The pathways elaborated so far mainly describe the fever and possibly also sleep-inducing effects of macrophage-derived interleukin-1, the astrocytes as antigen presenting cells and producers of interleukin-1 like factors, and the neuroimmune-endocrine interactions. By continuing these studies, it will be possible to provide significant proof to unlock the paradigm of the brains as an immunogically priviledged site.