Haptoglobin activates innate immunity to enhance acute transplant rejection in mice
Hua Shen, … , Margherita Maffei, Daniel R. Goldstein
Hua Shen, … , Margherita Maffei, Daniel R. Goldstein
Published December 12, 2011
Citation Information: J Clin Invest. 2012;122(1):383-387. https://doi.org/10.1172/JCI58344.
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Haptoglobin activates innate immunity to enhance acute transplant rejection in mice

Abstract

Immune tolerance to transplanted organs is impaired when the innate immune system is activated in response to the tissue necrosis that occurs during harvesting and implantation procedures. A key molecule in this immune pathway is the intracellular TLR signal adaptor known as myeloid differentiation primary response gene 88 (MyD88). After transplantation, MyD88 induces DC maturation as well as the production of inflammatory mediators, such as IL-6 and TNF-α. However, upstream activators of MyD88 function in response to transplantation have not been identified. Here, we show that haptoglobin, an acute phase protein, is an initiator of this MyD88-dependent inflammatory process in a mouse model of skin transplantation. Necrotic lysates from transplanted skin elicited higher inflammatory responses in DCs than did nontransplanted lysates, suggesting DC-mediated responses are triggered by factors released during transplantation. Analysis of transplanted lysates identified haptoglobin as one of the proteins upregulated during transplantation. Expression of donor haptoglobin enhanced the onset of acute skin transplant rejection, whereas haptoglobin-deficient skin grafts showed delayed acute rejection and antidonor T cell priming in a MyD88-dependent graft rejection model. Thus, our results show that haptoglobin release following skin necrosis contributes to accelerated transplant rejection, with potential implications for the development of localized immunosuppressive therapies.

Authors

Hua Shen, Yang Song, Christopher M. Colangelo, Terence Wu, Can Bruce, Gaia Scabia, Anjela Galan, Margherita Maffei, Daniel R. Goldstein

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Figure 3

Haptoglobin activates DCs via MyD88, and donor haptoglobin increases the tempo of acute skin transplant rejection.

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Haptoglobin activates DCs via MyD88, and donor haptoglobin increases the...
(A and B) Human haptoglobin was added to WT and Myd88–/– DCs and IL-6 and TNF-α measured (ELISA). *P < 0.01, t test. (C) C57BL/6 WT and Myd88–/– DCs were haptoglobin (100 μg/ml) or PBS treated, then transferred i.p. to BALB/c recipients (n = 3/group). At 21 days after transfer, recipient splenic T cells were stimulated overnight with C57BL/6 spleen cells and IFN-γ recorded (ELISPOT). *P < 0.001, t test. (D) IL-6 production by DCs (ELISA) after culture in necrotic lysates from haptoglobin–/– (hp–/–) or WT nontransplanted skin. *P = 0.001, t test. (E) hp–/– or WT male skin was transplanted onto WT female recipients and graft survival measured. Survival times between the 2 groups were different. P < 0.01, log rank. (F) Antidonor splenic T cell responses were measured after ex vivo stimulation with donor or recipient cells (ELISPOT) at day 21 after transplantation. All recipients were WT. *P < 0.0004, t test. (G) Histology of WT transplants (day 21 after transplantation) shows epidermal and dermal necrosis with abundant scale crust (upper panel, ×4; scale bar: 0.25 mm), with numerous inflammatory cells (lower panel, ×40; scale bar: 0.06 mm). hp–/– grafts exhibit less necrosis and inflammation. Representative samples, n = 3 mice/group. Data in A–D and F are representative of 1 experiment that was repeated independently once (C and F) or twice (A, B, and D) with consistent results. n = 3/group/experiment. Cell culture assays run in triplicate. Error bars represent SEM.