Sublethal infection of mice with Listeria monocytogenes has been shown to induce a protective CD8+ CTL response. In addition to the presentation of Listeria antigens by MHC class Ia molecules, recent studies show that the MHC class Ib molecules Qa-1 and M3 are also restriction elements for antilisterial CTL. We have infected C57BL/6 mice that lack MHC class Ia proteins (H-2Kb, Db) with Listeria to assess whether class Ib antigen presentation plays a significant role in generating CD8 effector cells to this pathogen. Uninfected B6 Kb-/- Db-/- mice have 2% CD8+ cells. On day 6 following i.v. infection with 2,000 CFU of Listeria, we observe a 3-4 fold expansion of splenic CD8+ cells. To determine if this expanded CD8+ population contains Listeria specific CTL, spleen cells were tested in a 51Cr release assay using target cells infected with viable Listeria. The macrophage cell line J774 (H-2d) is lysed by this effector population only upon Listeria infection, demonstrating the presence of MHC class Ib restricted antilisterial CTL. To identify the role of individual class Ib molecules, fibroblast cell lines transfected with Qa-1b or M3 were tested for sensitivity to lysis. Both were recognized and lysed upon Listeria infection, whereas the parental control cell lines were not. Our results demonstrate that in the absence of MHC class Ia proteins, presentation of L. monocytogenes antigens by MHC class Ib molecules in vivo is sufficient to generate a CD8+ CTL response. Experiments are underway to compare the efficiency of CD8 mediated class Ib restricted immunity to that restricted by class Ia molecules.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Molecular Biology