In vitro preparation and characterization of the human CD3 epsilon epsilon homodimer and CD3 epsilon gamma and CD3 epsilon delta heterodimers.

The CD3 molecule is a critical component of both humoral and cellular immune responses, and yet while the structure and molecular assembly of other key mediators such as CD4 and CD8 have been reported, individual CD3 subunits have not been well characterized. Our understanding of the manner in which they interact remains limited, and the question of how many subunits are required for a functional CD3 molecular complex is yet to be addressed. It has been suggested that CD3 epsilon pairs with CD3 gamma or with CD3 delta, forming CD3 epsilon gamma and CD3 epsilon delta heterodimers that associate with alpha/beta T cell receptors (TCRs) and CD3 zeta 2 dimers. In this study we investigated whether interactions between each CD3 epsilon subunit play a role in the formation of the CD3 molecular complex. Our results revealed that the human CD3 epsilon subunit forms a homodimer structure, which is a crucial piece of information for the elucidation of cellular signaling following TCR receptor ligation, and provide insight into our understanding of the molecular assembly of the CD3 molecular complex.