Session Time: 6:00pm-7:00pm
Presentation Time: 6:05pm-6:10pm
*Purpose: Longer cold ischemic storage (CIS) time prior to transplant results in increased proliferation of endogenous donor-reactive memory CD8 T cells within complete MHC-mismatched cardiac allografts at 24 hrs after transplant and in enhanced effector functions to mediate CTLA-4Ig-resistant rejection of the high-risk allografts. This increased memory CD8 T cell proliferation within high-risk allografts requires CD4 T cell help via CD40-CD154 interactions with graft dendritic cell (DC)s to produce IL-12p40 homodimer (p40 HD) that is a key factor for driving the memory CD8 T cell proliferation.
*Methods: Here, we investigated how p40HD stimulate endogenous memory CD8 T cell proliferation within high-risk allografts.
*Results: When testing the impact of p40HD on cytokine production in the allografts, p40 HD injection into recipients of low-risk allografts induced marked increases in graft IL-15. Consistent with this, the longer CIS time increased mRNA expression of IL2Rα (CD25), IL2Rβ(CD122) and IL15Rα in purified CD8 T cells infiltrating the allografts on day 2 post-transplant and markedly increased IL-15 protein in the allografts. Blocking IL-15 signaling with anti-CD122 mAb inhibited endogenous memory CD8 T cell proliferation within high-risk allografts at 48 hrs after transplant and prolonged allograft survival in CTLA-4Ig conditioned recipients to that observed in CTLA-4Ig conditioned recipients of low-risk allografts. Moreover, anti-CD122 mAb inhibited p40HD induced memory CD8 T cell proliferation within low-risk allografts. To test the source of IL-15, we transplanted diphtheria toxin (DT) receptor-CD11c transgenic mice subjected to 8hr CIS into A/J recipients. Depletion of CD11c+ cells abrogated the p40HD-induced endogenous memory CD8 T cell proliferation and IL-15 production within low-risk allograft. To further test the role of allograft IL-15 signaling, we used B6.IL15Rα-/- as donors. Graft deficiency of IL-15Rα decreased the endogenous memory CD8 T cell proliferation within allografts at 48 hrs post-transplant and extended survival of grafts in CTLA-4Ig conditioned recipients.
*Conclusions: These results indicate that p40 HD produced by graft DCs stimulate graft DCs to produce IL-15 that directly drives endogenous donor-reactive memory CD8 T cell proliferation to mediate CTLA-4 resistant rejection. The IL-15 mediated regulation of endogenous memory CD8 T cell may provide a new strategy to attenuate CTLA-4Ig resistant rejection mediated by these donor reactive T cells.
To cite this abstract in AMA style:Tsuda H, Valujskikh A, Fairchild R. P40 Homodimers Induce Il-15 to Promote Endogenous Donor-reactive Memory Cd8 T Cell Activation within High-risk Cardiac Allografts [abstract]. Am J Transplant. 2021; 21 (suppl 3). https://atcmeetingabstracts.com/abstract/p40-homodimers-induce-il-15-to-promote-endogenous-donor-reactive-memory-cd8-t-cell-activation-within-high-risk-cardiac-allografts/. Accessed September 23, 2021.
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