CD226 and primary progressive multiple sclerosis: A: An age-dependent decrease in the expression of immunoinhibitory molecules (KLRG1, LAG3, CTLA-4 on memory CD8 T cells) was abrogated in MS T cells of old patients with MS displayed increased intracellular expression IFN-γ and TNF-α on stimulationControls exhibited a strong age-dependent increase in costimulatory molecule CD226 on memory and EM CD8 T cellsB: An age-dependent decrease in counts of lymphocytes, B and T cells and NK cells in patients with PPMS