INDUCTION OF INCREASED GRAFT-VERSUS-HOST DISEASE BY MOUSE SPLEEN CELLS SENSITIZED IN VITRO TO ALLOGENEIC TUMOR

Abstract

The aim of this study was to sensitize cells in vitro, follow their proliferative and cytotoxic responses, and determine their ability to cause lethal graft-vs.-host disease (GVHD). C57BL/6 (H-2b) spleen cells were incubated with irradiated BALB/c (H-2d) Moloney lymphoma cells (LSTRA) in mixed leukocyte culture conditions for 2, 4 or 6 days and then tested. The maximal proliferative response occurred after 4 days. In vitro cytotoxic reactivity against 51Cr-labeled LSTRA was generated by 4 days (76.3 .+-. 3.1% 51Cr released) and 6 days (133.0 .+-. 4.8%) of sensitization but not by 2 days (-0.2 .+-. 1.1%). Induction of fatal GVHD was assayed by injecting graded doses of the C57BL/6 spleen cells i.v. into adult BALB/c mice pretreated with cyclophosphamide, 180 mg/kg. Cells sensitized for 2 days were effective but no more so than were (control) cells cultured with irradiated C57BL/6 spleen cells. Cells sensitized longer were far more active than the control cells. Cells sensitized for 4 days killed 70 of 88 mice (80%), and those sensitized for 6 days killed 37 of 48 mice (77%), whereas control cells killed only 42 of 90 mice (47%) (P < 0.005). Thus, cells sensitized in vitro exhibited an increased ability to induce GVHD in vivo, which was temporally associated with the development of cytotoxicity in vitro.