The T-cell antigen receptor (TCR) exists in monomeric and nanoclustered forms
independently of antigen binding. Although the clustering is involved in the regulation of T-
cell sensitivity, it is unknown how the TCR nanoclusters form. We show that cholesterol is
required for TCR nanoclustering in T cells and that this clustering enhances the avidity but
not the affinity of the TCR-antigen interaction. Investigating the mechanism of the
nanoclustering, we found that radioactive photocholesterol specifically binds to the TCRβ …