Abstract: The present invention relates to modified T cell receptors (TCRs) and to their use in adoptive cell therapy (ACT), in particular for the transfer of T lymphocytes. The TCRs are mutated in the transmembrane regions of the alpha and beta chains with mutations favoring the correct TCR chain pairing. The correct pairing of the transferred exogenous alpha and beta TCR chains improves the functional activity and safety of the genetically modified T cells for the therapy of tumours and infectious diseases. The invention also relates to T cell receptor alpha or beta chain, to a recombinant TCR, a TCR complex, a nucleic acid coding for the TCR alpha or beta chain, to relative recombinant expression vector, host cells, pharmaceutical composition and to a method of detecting a hematological malignant cell, a solid tumor cell or an infected cell.