Population of lymphoid tissues in cured W-anemic mice by donor cells.

The percentages of donor cells in lymphoid organs of cured W-anemic mice were determined by using donors with the T6 chromosome marker. W-anemic recipients of two different genotypes were cured by marrow or spleen grafts from histocompatible normal T6/T6 or T6/+ donors. After 2 to 10 months, almost all proliferating cells in the thymuses and marrows, and approximately 75% in the spleens of cured mice were of donor type. However, only 30-40% of the proliferating cells in recipient lymph nodes and 10-20% in their Peyer's patches were of donor type. Percentages of donor cells in marrows and spleens remained high hemopoietic cell division was stopped by injections of erythrocytes. All tissues were slightly less repopulated by donor cells in W-anemic recipients cured by spleen cells compared with those cured by marrow cells. These results were not altered by matching recipients and donors to avoid possible graft versus host reactions, or by removing the thymus of a recipient before it was cured. The fact that the repopulating cells are not all donor type suggests that there are at least two classes of precursor cells that populate the immune system of W-anemic mice, and that not all classes are derived from the grafted cells. Cured W-anemic mice may provide a unique system in which different types of precursor cells of the lymphoid system can be distinguished.