The T lymphocyte lineage, from initial stem cells to peripheral mature T-cells, are members of a highly reactive cell system engaged in the control of internal homoeostasis and body intactness. It fulfills its commitments in close communication with the cellular and non-cellular microenvironment and with neuroendocrine regulatory mechanisms. Tools of such communication are various substances and compounds identified as cytokines, chemokines, hormones, growth factors and neuropeptides. Any pathogenetical model of functional aberration and disease development in the T-cell system must take into account the delicate network control exerted by the above mechanisms. In the following we describe the major players in the network regulation of T-cell development and function as a basis for a computational modeling study.