Organ specificity of c-kit+ lymphoid precursors in the liver, thymus, and bone marrow.

c-kit+Lin- cells are present in various immune organs, including the liver, thymus, and bone marrow, where lymphoid, myeloid, or erythroid cells are generated. To compare their properties as lymphoid precursors, c-kit+Lin- cells purified from various organs of B6.Ly5.1 mice were injected into 6.5 Gy-irradiated B6.Ly5.2 mice. Depending on the source of the c-kit cells, the degree of entrance and expansion of lymphoid cells differed in the liver and thymus of recipient mice. c-kit+ cells isolated from the bone marrow entered and expanded prominently in both the liver and thymus, whereas c-kit+ cells from the thymus did not do so at all. On the other hand, c-kit+ cells isolated from the liver and spleen showed an intermediate pattern, namely, they took a long time to enter and expand in the liver and thymus of recipient mice. All of these c-kit+ cells had the potential to give rise to lymphoid cells, which were specific to the liver and thymus, respectively. We previously showed that progenitor cells for extrathymic T cells in the liver and those for conventional T cells in the thymus are not always supplied by the bone marrow, as shown by experiments using parabiosis. Taken together with those previous data, the present results suggest that c-kit+Lin- cells isolated from various immune organs have organ specific properties.