Targeting LFA-1 Synergizes with CD40/CD40L Blockade for Suppression of Both CD4-Dependent and CD8-Dependent Rejection

Abstract

Allogeneic hepatocytes elicit CD4-dependent and (CD4-independent) CD8 + T-cell-initiated graft rejection. The (CD4-independent) CD8 + T-cell pathway is resistant to immunosuppressive strategies that readily and indefinitely suppress CD4 + T-cell-dependent rejection responses. Consequently, successful immunoregulation of hepatocyte-initiated immune responses requires a strategy which regulates both CD4-dependent and CD8-dependent rejection responses. Interference with CD40/CD40 ligand (CD40L) costimulation only transiently suppresses CD4-and CD8-dependent hepatocyte rejection. Interference with CD28/B7 costimulation transiently suppresses CD4-dependent hepatocyte rejection, but is ineffective for suppression of CD8-dependent hepatocyte rejection. To date, hepatocyte survival > 60 days post-transplant has not been achieved by any immunotherapeutic strategy. In the current study, we evaluated a novel immunosuppressive strategy which targets both LFA-1 and CD40L-mediated signals. Targeting LFA-1 suppressed (CD4-independent) CD8 + T-cell-initiated hepatocyte rejection such that allogeneic hepatocyte survival > 60 days was achieved in 70% of CD4 KO mice. Targeting both LFA-1-mediated signals and CD40/CD40L costimulation resulted in synergistic effects, such that hepatocellular survival > 60 days was achieved in 100% of C57BL/6 mice (which have both CD4-and CD8-dependent T-cell pathways available).

Targeting LFA-1 and CD154 Suppresses the In Vivo Activation and Development of Cytolytic (CD4-Independent) CD8+ T Cells

“…Furthermore, combined blockade of CD40/CD154 and LFA-1 resulted in long-term hepatocyte allograft survival in 80% of recipients (3). This is the first strategy identified which indefinitely suppresses CD8-dependent hepatocellular allograft rejection across a complete MHC mismatch.…”

“…H epatocellular allografts have previously been demonstrated to initiate both CD4 ϩ T cell-dependent and (CD4 ϩ T cell-independent) CD8 ϩ T cell-dependent pathways of allograft rejection (1)(2)(3)(4). The activity of the latter CD8-dependent rejection pathway can be demonstrated following transplantation of hepatocellular allografts into CD4 knockout (KO) 4 mice (1), CD4-depleted C57BL/6 mice (2), and CD8-reconstituted SCID mice (1,4).…”

“…The CD8-dependent pathway of rejection occurs not only in response to hepatocellular allografts (1)(2)(3)(4), but also in response to intestinal allografts (10 -12), and, under particular experimental conditions, to skin allografts (9,13) and cardiac allografts (7,8). These studies consistently demonstrate that this pathway is resistant to immunoregulation with strategies that are very effective at suppressing CD4-dependent immune activation such as Rapamycin (14), Cyclosporine (15), anti-CD4 mAb (7,9,16), gallium nitrate (16), anti-CD154 mAb (7,9,11), combined treatment with donor-specific transfusion and anti-CD154 mAb (5,17), and CTLA4-Ig (6,9,10).…”

Combinations of Anti-LFA-1, Everolimus, Anti-CD40 Ligand, and Allogeneic Bone Marrow Induce Central Transplantation Tolerance through Hemopoietic Chimerism, Including Protection from Chronic Heart Allograft Rejection

“…Although costimulation through LFA-1 was shown to contribute to IL-2 production, cell cycle progression, and effector functions of both CD8 and CD4 T cells (46 -49), CD8 T cells appeared to be more sensitive to LFA-1-mediated costimulation (50,51). A recent study using allogeneic hepatocyte transfer in CD4-and CD8-deficient mice demonstrated the relevance of both CD40L and LFA-1 costimulation pathways for both alloreactive CD4 and CD8 T cells, albeit with a stronger influence of LFA-1 than CD40L on costimulation for CD4-independent CD8-dependent alloreactivity (52). In the context of hemopoietic chimerism, selective CD4 and CD8 depletion experiments revealed that anti-CD40L could overcome CD4 but not CD8 T cell-dependent resistance to allogeneic BM engraftment (53).…”

MHC Disparate Resting B Cells Are Tolerogenic in the Absence of Alloantigen-Expressing Dendritic Cells

“…Depletion of CD4 + T cells or CD8 + T cells, or both, from the peripheral blood was >98% in all mice, as assessed by �ow cytometry (FACScan, Becton Dickinson). In studies evaluating the role of CD40-CD40L interactions, MR1 (anti-CD40L mAb, 250 g/mouse) was injected into ATX FVB mice on days -14, −10, −7, −3, 0, 4, and 7 and twice weekly thereaer, with respect to skin transplantation [15]. Anti-D …”