Isolation of CD45RO(+), memory T cells recognizing proteolipid protein from neurologically normal subjects

Previous studies provide evidence for in vivo activation of MBP-reactive T cells in subjects with multiple sclerosis. In general, in vivo activation o ccurs less frequently in healthy control subjects. In the current study we examined the T cell response to proteolipid protein in PBMC isolated from 9 control subjects. We used CD45 isotypes as markers for memory and naive T cells to assess in vivo activation of CD4(+) T cells reactive with PLP. In contrast to the results obtained using MBP, we found that approximately 50% of PLP-reactive T cells were derived from the CD45RO(+) memory subpopulati on of T cells isolated from these control subjects. These results indicate that some myelin-reactive T cells have undergone activation in vivo in neur ologically intact individuals. This suggests that immunoregulatory mechanis ms may be present that prevent overt disease in spite of in vivo activation of PLP-reactive T cells. (C) 2001 Academic Press.