The xid mutation affects hemopoiesis in long term cultures of murine bone marrow

Cells of the humoral immune system are particularly affected by a mutation at the X chromosome linked immunodeficiency disease (xid)locus. Although B cells are made in normal numbers, they fail to become phenotypically and functionally diverse. Consequently, poor antibody responses are mounted to certain types of Ag. There have been some indications that other types of hemopoietic cells may be influenced by the mutation and development of the humoral immune system is unusually dependent on the presence of T lymphocytes. We now describe an analysis of the lympho-hemopoietic environment studied with long term bone marrow cultures. Contrary to expectations, cultures initiated with cells from homozygous female or hemizygous male mice with the mutant allele established more quickly than normal. The accelerated initial growth pattern was clearly linked to the xid mutation. Artificial mixtures of marrow exhibited intermediate growth kinetics. Experiments with H-2 congenic and T6 chromosome marked cells did not reveal an intrinsic dominance of growth in nonadherent xid cells. Similar results were obtained with culture conditions which favored production of myeloid or lymphoid cells. These findings would be consistent with subtle changes in the bone marrow microenvironment resulting from the xid mutation. The pedigree of the mouse strains had a significant influence on lymphopoiesis in long term bone marrow cultures. Lymphocytes of BALB/c origin dominated over CBA/H background cells in cultures established from mixtures of the two, but this did not correlate with any functional deficiency in CBA/H stromal cells. In fact, establishment of an adherent layer was a rate-limiting step in initiating long term cultures and this could be achieved with a low dose inoculum of CBA/H marrow. Even more dramatic effects were found in hemopoietic cells from doubly defective C3H.nu/nu-xid mice. The bone marrow of these athymic animals contained normal numbers of granulocyte/macrophage progenitors. However, lymphoid cultures could not be reproducibly established with their cells and myelopoiesis was never observed in vitro. The relatively simple conditions which pertain in culture make it possible to appreciate effects of mutations and pedigree on hemopoiesis which are unremarkable in intact animals.