Macrophages induce long-term trapping of γδ T Cells with innate-like properties within secondary lymphoid organs in the steady state

So far, peripheral T cells have mostly been described to circulate between blood, secondary lymphoid organs (SLOs), and lymph in the steady state. This nomadic existence would allow them to accomplish their surveying task for both foreign Ags and survival signals. Although it is now well established that γδ T cells can be rapidly recruited to inflammatory sites or in certain tumor microenvironments, the trafficking properties of peripheral γδ T cells have been poorly studied in the steady state. In the present study, we highlight the existence of resident γδ T cells in the SLOs of specific pathogen-free mice. Indeed, using several experimental approaches such as the injection of integrin-neutralizing Abs that inhibit the entry of circulating lymphocytes into lymph nodes and long-term parabiosis experiments, we have found that, contrary to Ly-6C^-/+CD44^lo and Ly-6C⁺CD44^hi γδ T cells, a significant proportion of Ly-6C^-CD44^hi γδ T cells are trapped for long periods of time within lymph nodes and the spleen in the steady state. Specific in vivo cell depletion strategies have allowed us to demonstrate that macrophages are the main actors involved in this long-term retention of Ly-6C^-CD44^hi γδ T cells in SLOs.