Phosphorylation at Ser76 does not regulate T-cell proliferation or CD43 exclusion from the immune synapse. (A,B) Resting DO.CD43^−/− T cells transduced with (A) CD43-FL or (B) CD43-Ser76Ala constructs were labeled with CFSE and stimulated with OVA_323-339-pulsed A20 B cells. Proliferation was measured by CFSE dilution. For each CD43 construct, transduced cells (CD43⁺) are compared with untransduced cells (CD43⁻). Inset depicts the MFI of CD43 expression on cells transduced with CD43-FL (solid lines) or CD43-Ser76Ala (dotted lines). (C) Transduced cells were conjugated with OVA_323-339-pulsed A20 cells, fixed, and stained for CD43. (D) Data representing percentage of cells in conjugates that have excluded CD43 are shown. Data are the mean (± SEM) from 3 independent experiments with 50 conjugates each (ns = not significant). In the absence of peptide, less than 10% of conjugates exclude CD43 (data not shown).