The mean geometric mean fluorescence intensity of HLA class I on LCL was 434 (173) in healthy subjects and 425 (173) in patients with MS (p = 0.82), showing that the decreased T cell reactivity to LCL in patients with MS was not due to decreased HLA class I expression on LCL and was most likely due to an absolute decrease in the numbers of CD8+ T cells reacting to LCL. The gene discussed is CD8A; the disease is myeloid sarcoma.