Anti-Parental-Strain Lymphocyte Responsiveness of F1 Hybrid-Strain Lymphocytes

The interactions between immunocompetent parental-strain tells and the F₁ hybrid rat into which these cells have been injected were studied. This involved examination of the behavior of both parental- and host-strain cells. Host lymphocytes reactive against parental-strain lymphocytes appeared in the thoracic duct lymph within 12 h of the intravenous injection of parental thoracic duct lymphocytes or thymus cells. The activity of these F₁ hybrid-strain lymphocytes was directed preferentially against parental-strain lymphocytes with anti-F₁ hybrid potential. This subpopulation of parental cells was absent from the thoracic duct but was well represented in the spleen, this enrichment being masked by a reversible F₁ hybrid anti-parental-strain lymphocyte response. If the anti-parental-strain lymphocyte activity of F₁ hybrid cells was interrupted by the destruction of host-strain cells with antiserum, parental-strain lymphocytes in the tissues of F₁ hybrid rats could be reactivated. By this procedure it was possible to passage graft-versus-host reactions initiated by parental-strain lymphocytes through several F₁ hybrid rats, thereby implying that anti-parental lymphocyte activity is of importance in limiting the serial passage of these reactions. Some of the anti-parental lymphocyte activity observed on the part of F₁ hybrid-strain cells was probably mediated by anti-idiotypic antibodies, but other phenomena, especially selective migration of both donor and host lymphocyte subpopulations, are of major importance in the interaction between parental-strain lymphocytes and an F₁ hybrid host.