The team of Simon Fillatreau identified in a collaborative work with the team of Dr. Nadine Hövelmeyer (Mainz University, Germany) the chief role of the AKT-FoxO1 signaling axis in the formation of mouse and human marginal zone B cells, which are involved in host defense against encapsulated bacteria (Cell Reports, doi: 10.1016/j.celrep.2023.112378). Remarkably, AKT signaling also conferred B cells with increased innate function, a distinctive functional property of marginal zone B cells, thus linking the signals controlling the development of these cells to their function. Furthermore, they identified CD148 as a receptor present at higher level on the surface of marginal zone B cells in mice and humans, compared to other B cell subsets, and whose expression in B cells is controlled by AKT signaling intensity, potentially providing a key to evaluate AKT signaling and track innate B cells.