[Regulation of cell growth exemplified by T lymphocytes]

The aim of this paper is to describe the complexicity of growth regulation, particular of T-lymphocytes. Different surface molecules are known, which trigger the process of cell activation after binding of the respective ligands, including the T-cell-receptor/CD3 complex, the CD2 and the CD4 molecules. This surface molecules induce among other cellular events the expression of additional receptors, such as IL-2-receptors and Transferrin-receptors. The structure of these surface molecules, their possible functions and involved mechanisms of signal transmission from the membrane to the level of gene expression are presented. The different mechanisms of signal transmission and structures involved, such as the G-protein, are discussed. The different systems of signal transmission, in which such enzymes like Ca2+-dependent neutral Protease, Phospholipase C, Adenylatcyclase, Phospholipase A2 and Proteinkinases are involved, can interact. The regulation of the proliferation of T-cells is the result of a common action of different lymphokines, but also of growth factors from non-immune cells.