CD69+ memory T lymphocytes of the bone marrow and spleen express the signature transcripts of tissue-resident memory T lymphocytes

It is a matter of current debate whether the bone marrow is a hub for circulating memory T lymphocytes and/or the home of resident memory T lymphocytes. Here we demonstrate for CD69 murine CD8 , and CD69 murine and human CD4 memory T lymphocytes of the bone marrow, making up between 30 and 60% of bone marrow memory T lymphocytes, that they express the gene expression signature of tissue-resident memory T lymphocytes. This suggests that a substantial proportion of bone marrow memory T lymphocytes are resident. It adds to previous evidence that bone marrow memory T cells are resting in terms of mobility and proliferation, and maintain exclusive long-term memory to distinct, systemic antigens.