Studies on hyperlymphoid mice.

Injection of syngeneic, but chromosomally distinguishable, lymph node or spleen cells into adult mice resulted in both T- and B-lymphocyte chimaerism. In spleen-injected mice haematopoietic chimaerism was also established. It appeared that the donor T lymphocytes were added to the host recirculating T-cell pool so that a hyperlymphoid state was produced. The percentage of donor T lymphocytes declined very slowly in normal mice, but remained stable in adult-thymectomized animals. There was no evidence of a homeostatic mechanism involving destruction of excess peripheral T lymphocytes or grossly affecting the flow of T lymphocytes from the thymus into the recirculating T-cell pool. A preliminary model of the T-lymphocyte system is proposed.