FORMATION OF TCR DIMERS TRIMERS AS A CRUCIAL STEP FOR T-CELL ACTIVATION/

T cell activation involves specific interactions between the TCR and p eptides presented by the MHC. This engagement leads to phosphorylation and subsequent internalization of the TCR complex. By analyzing the k inetics of the internalization of TCR, we found that the rate of TCR d own-regulation was proportional to the square of the TCR density. Math ematical modeling of TCR interactions indicates that such a relation i s only possible if TCR dimerize before internalization. By mathematica l analysis, our data would also be compatible with trimer but not larg er oligomer formation. Thus, minimal TCR oligomerization is an essenti al step for peptide-mediated T cell activation.