In humans, it is postulated that the transitional cells, after leaving the bone marrow, are subjected to peripheral checks to prevent the production of autoantibodies.
[4][5] All transitional B cells are high in heat-stable antigen (HSA, CD24) relative to their mature counterparts and express the phenotypic surface markers AA4.
[7] As in the mouse, human transitional cells can be found in the bone marrow, peripheral blood, and spleen.
However, in contrast to the nuanced models proposed in the mouse, thus far human studies have, by and large, described a rather homogeneous population of transitional B cells (T1/T2) defined by the expression of high levels of CD24, CD38 and CD10.
[1][8] Overall there is general agreement on the markers used to separate the subpopulations, although some differences exist in the number of subgroups and in the functional characteristics of the T2 population.