DONOR-HOST CELL INTERACTION IN HOMOLOGOUS SPLENOMEGALY IN THE CHICK EMBRYO

¹ Department of Zoology, University of Maine, Orono, Maine

1. Adult chicken spleen from a highly inbred line (Line 7) was implanted on the chorioallantoic membrane of embryos from the same line. When the host spleen was transferred to the chorioallantoic membrane from a different strain, a striking enlargement was obtained, which suggested that adult donor cells were transferred from the first host.

2. When the first host was derived from a different line, and the host spleen was then transferred to another host of the same line as the adult donor, a striking enlargement of the host spleen was observed. This suggests that both adult and host cells were transferred to the second host and also that proliferation of the host embryonic component may have occurred.

3. The splenomegaly phenomenon was inhibited by the intravenous injection of 5-fluorouracil following the implantation of adult chicken spleen. However, the unenlarged host spleen, when transferred to another host embryo, was able to elicit splenomegaly. This reveals the presence of viable and competent donor cells in the treated host spleen.

4. When a fresh piece of 17-day-old chick embryo spleen was added to the chorioallantoic membrane of an embryo which had previously received a graft of adult spleen and an injection of 5-fluorouracil, a significant enlargement of the second embryonic spleen graft was observed.

5. These observations suggest that the splenomegaly reaction is due in part to the proliferation of host embryo cells following stimulation by the adult donor cells.