During lymphatic regeneration, precursors for major histocompatibility complex-restricted cytotoxic T cells appear before alloreactive precursors.

Mice were injected with a sublethal dose of cyclophosphamide (Cy) (300 mg/kg), and the appearance of the capacity of the regenerating spleen to form cytotoxic T lymphocytes (CTL) in response against 2,4,6 trinitrophenyl-coupled syngeneic cells or against allogeneic cells was followed. It was found that 8 da after Cy injection, the spleen contained cells that could give rise to CTL, but only 2,4,6 trinitrophenyl-specific CTL responses could be obtained at this stage. A low alloresponse was first seen 2 wk after Cy injection.