There is a well-defined influence of dopamine (DA) within the immune system. It can be synthesized not only in neurons, but also in immune cells, especially in T cells. In addition, these cell are bearing an active uptake mechanism, which could serve another source of DA. Therefore, it is highly likely that a functional DA-erg autocrine/paracrine regulatory loop exists, where lymphocytes-derived DA acting through its own receptors, also expressed on the same cells, can have an influence on its own function. However, the possibility that immune cell derived DA may act in accordance with DA secreted by other sources, i.e. from sympathetic terminals, cannot be ruled out. In harmony with these observations have provided evidences for the existence of a functional DA-erg system in the thymus, indicating that DA may have also a role in the maturation and selection of a certain subpopulation of lymphocytes as well. Based upon all of this information and evidences, for being able to summarize this topic, a much broader survey, including all direct and indirect immune-modulatory role of DA is required. Therefore, in this review we are going to discuss the most relevant aspects of this regulatory function. Facts and theories based upon experimental (pre-clinical) data are extended with the evidences accumulated by clinical observations.