The immune system is vigilant in detecting foreign pathogens. Our cells present peptides (p) atop Major Histocompatibility Complex (MHC) glycoproteins. These pMHC molecules are displayed on the cell’s surface and monitored by T cells of the immune system that patrol the body. T cells use their specialized T cell receptors (TCRs) to recognize and bind to pMHCs, where the quality of binding influences T cell activation. Activated T cells are responsible for killing off infected cells and clearing infection. The contribution of individual parameters that dictate activation for this cell-to-cell TCR-pMHC interaction are unclear. However, a long reigning hypothesis is that the threshold of T cell activation can be determined by the dissociation constant or binding affinity. We have engineered a disulfide bond (DSB) between two cysteine residues introduced into a TCR and peptide that are known to form a TCR-pMHC complex. The formation of the DSB was validated using biophysical assays and X-ray crystallography. This approach represents a model in which the covalently bonded TCR-pMHC does not dissociate, prolonging the confinement time of the interaction. Formation of the DSB between APC and T cells in vitro translated to a 50-fold increase in T cell sensitivity compared to the wild-type counterpart, without altering binding affinity. Thus, we show that confinement time plays an important role in the activation of T cells, which could be useful in designing T cell therapies or peptide vaccines.