In CIBSS we work on engineering the T cell receptor (TCR). This receptor is a multiprotein complex, including the protein CD3gamma. In this publication we have contributed to work by the group of Regueiro in Spain, in which we analysed the contribution of different domains of CD3gamma to TCR formation and signaling by reconstituting the receptor using chimeric CD3gamma molecules. We demonstrate that assembly of the TCR dependent on the extracellular domain of CD3gamma and could not be replaced by the one of the very similar CD3delta. Signalling in form of the response to phorbolesters maps to the cytoplasmic domain of CD3gamma. Further, this CD3gamma domain was required for TCR-induced optimal IL2 and TNFa production and CD69 expression, indicating that a TCR without a CD3gamma cytosolic domain has altered signalling capabilities.