Immune response to Moloney-murine leukemia virus-induced antigens in bone marrow

By exploring induction and persistence of virus-specific memory CD8+ T cells in the BM of Moloney-murine sarcoma/leukemia virus-immune mice, we observed that the amount of activated CD8+CD62L− cells increased more rapidly and persisted for a longer period than in peripheral organs. Among the CD8+CD62L− subset, the few cells, specific for M-MuLV encoded antigens, expressing TCRVβ5 rearrangements increased in an explosive manner doubling the percentage of TCRVβ5+ subset so that as a final result more than 10% of CD8+ lymphocytes became potential virus-specific cytotoxic effectors. The numerical expansion of Vβ5+ cells started and persisted in the same proportion among both CD8+CD62L− and CD8+CD62L+ subsets. In these subsets the analysis of CD44 phenotype, to distinguish effector (TEM) and central (TCM) memory, evidenced a twofold increase of Vβ5+ TEM percentage and fourfold increase of Vβ5+ TCM. In parallel, the non virus-specific Vβ5− counterpart, also numerically increased due to the CD8+ expansion, was partially reduced as TEM percentage and doubled as TCM percentage. We conclude that the immune response to M-MuLV encoded antigens in BM generate not only a large number of virus-specific memory cells but also the re-shaping of the entire memory T cell repertoire.