Persistence of regulation mechanism responsible for inhibition of allotransplantation reactions in the absence of alloantigen.

The purpose of the present work was to examine the persistence of regulatory cells implicated in the inhibition of allotransplantation reactions in recipient mice in the absence of antigenic material. Two experimental systems were used: (1) When neonatally induced tolerance (obtained as a result of cell-free spleen extract administration in the B10.D2 versus M504 strain combination) was adoptively transferred, the persistence of suppressor cells was detected in secondary recipients receiving a second homograft as long as 30 days after removal of a first homograft to the tolerance inducing haplotype. The removal of the skin homograft presenting a source of antigen for 60 days, resulted in tolerance interruption when a second test graft was applied. (2) When tolerance was induced in CBA mice with spleen-cell antigenic extracts and CFA and spleen cells from such animals were transferred to secondary recipients the following results were observed: Secondary recipients grafted with SaI tumour cells derived from the tolerance inducing A strain 20 days after tolerance induction presented an enhanced tumour growth. The adoptive transfer of this effect was at least partly due to IJ+ lymphocytes, since their removal reduced adoptive enhancement. However, if the cell transfer was delayed for 56 days after tolerance induction, the depletion of IJ+ or Thy 1.2+ cells did not affect the capacity of spleen cells to cause an enhanced growth of the homografted SaI cells. A delay of 100 days following donor enhancement induction did not result any adoptive transfer of SaI enhancement.