Rapid Conversion of Effector Mechanisms from NK to T Cells during Virus-Induced Lysis of Allogeneic Implants In Vivo

Abstract

Viral infections can strongly stimulate both NK cell and allospecific CD8 T cell responses, and these same effector cells can lyse allogeneic cell lines in vitro. However, the impact of viral infections on the effector systems mediating rejection of allogeneic tissues in vivo has not been fully explored. Using in vivo cytotoxicity assays, we evaluated the effector systems mediating the rejection of CFSE-labeled allogeneic splenocytes after an infection of C57BL/6 (B6) mice with lymphocytic choriomeningitis virus. Naive B6 mice predominantly used a NK cell-effector mechanism to reject allogeneic splenocytes because they rejected BALB/C (H2d) splenocytes but not CBA (H2k) splenocytes, and the rejection was prevented by immunodepletion of NK1.1+ or Ly49D+ NK cells. This rapid and efficient in vivo cytotoxicity assay recapitulated the specificity of NK cell-mediated rejection seen in longer duration in vivo assays. However, as early as 1 day after infection with lymphocytic choriomeningitis virus, a CD8 T cell-dependent mechanism participated in the rejection process and a broader range of tissue haplotypes (e.g., H2k) was susceptible. The CD8 T cell-mediated in vivo rejection process was vigorous at a time postinfection (day 3) when NK cell effector functions are peaking, indicating that the effector systems used in vivo differed from those observed with in vitro assays measuring the killing of allogeneic cells. This rapid generation of allospecific CTL activity during a viral infection preceded the peak of viral epitope-specific T cell responses, as detected by in vivo or in vitro cytotoxicity assays.

Expansion of Effector Memory TCR Vβ4+CD8+ T Cells Is Associated with Latent Infection-Mediated Resistance to Transplantation Tolerance

“…Previous work from Kean et al showed that NK cells represent a potent barrier to engraftment of allogeneic BM (31). Also, studies have shown that NK cells respond early after infection and that certain viral infections can strongly stimulate NK cells and can lyse allogeneic cells (36,37). With respect to ␥HV68 infection, Usherwood et al found that even though NK cells contributed little to control of infection, their numbers increase upon infection in mice with ␥HV68 (38).…”

“…2). Previous work from other groups has shown that NK cells respond early after infection and that certain viral infections can strongly stimulate NK cells and can lyse allogeneic cells (36,37). Also, NK cells have been shown to act as a barrier to tolerance induction and that their numbers increase upon infection in mice with ␥HV68 (31,38).…”

Different Mechanisms Control Peripheral and Central Tolerance in Hematopoietic Chimeric Mice

“…The in vivo cytotoxicity assay was performed as previously described (34 (35) to permit quantification of alloreactive CD8 + T-cell cytotoxicity in the absence of NK cell killing. Specific lysis was calculated as described (34).…”

Type 1 IFN Mediates Cross-Talk between Innate and Adaptive Immunity That Abrogates Transplantation Tolerance

“…Then, on the scheduled day of transplantation, they were not given grafts but instead analyzed for their ability to rapidly kill allogeneic target cells using an in vivo cytotoxicity assay. In this assay, rapid clearance of allogeneic cells in NK cell-depleted mice is indicative of effector CTL activity (29).…”

“…The in vivo cytotoxicity assay was performed as described elsewhere (29). Briefly, single-cell suspensions were prepared from spleens that were obtained from C57BL/6 (H2 b , syngeneic) or BALB/c (H2 d , allogeneic) mice.…”