Inflammation is known to preclude tolerance after
transplantation. We have previously shown that systemic
inflammation in xenograft recipients (SIXR) precedes activation of coagulation in the absence of T cell responses. Accordingly, SIXR may amplify innate and adaptive immune responses against xenografts after pig-to-primate
xenotransplantation, even with efficient immunosuppressive therapy. We evaluated the impact of
anti-inflammatory agents on pro-inflammatory
cytokines and
chemokines in pig artery patch and heart xenograft recipients. Baboons received an artery patch (Group1, n=8) or heart (Group2, n=4) from genetically engineered pigs. All baboons received lymphodepletion with
thymoglobulin (ATG) and costimulation blockade-based immunosuppression (anti-CD40 and/or CTLA4Ig). In Group1, baboons received either (i) no
anti-inflammatory agents (n=2), (ii)
cobra venom factor (CVF, n=2), (iii) α1-antitrypsin (AAT, n=2), or (iv)
interleukin (IL)-6 receptor antagonist (IL-6RA, n=2). In Group2, all baboon received
corticosteroids, either without (n=2) or with (n=2) IL-6RA. Serum IFN-γ, TNF-α, IL-1β,
IL-17,
IL-6,
IL-8, MCP-1, and sCD40L levels were measured by Luminex.
Fibrinogen, D-dimers, and
C-reactive protein (C-RP) were also measured. Recipient baboon T cell proliferation was evaluated by mixed lymphocyte reaction (MLR) before and after
transplantation. Pig and baboon
tissue factor (TF)
mRNA levels in heart xenografts were measured by RT-PCR. In no recipient was a marked increase in T cell response to pig cells observed after
transplantation. In Groups 1 and 2, post-
transplantation levels of IFN-γ, TNF-α, IL-1β, and
IL-17 remained comparable to or lower than pre-transplant levels, except in one heart recipient that succumbed to CMV
infection. In Group1, when no
anti-inflammatory agent was administered, post-transplant levels of
IL-6,
IL-8, and MCP-1 were elevated. After CVF,
IL-6,
IL-8, and MCP-1 remained low. After IL-6RA,
IL-6 and MCP-1 were elevated. After AAT,
IL-8 was elevated. sCD40L became elevated intermittently in most recipients irrespective of the administered
anti-inflammatory agent. In Group2,
IL-6 was transiently elevated, particularly after IL-6RA administration. MCP-1 gradually increased by 2 months in Group2 recipients. sCD40L generally remained low except in one recipient. In Group1 and Group2 recipients, C-RP levels were elevated except after IL-6RA administration, while D-dimers were elevated regardless of administration of
anti-inflammatory agent. In Group2, pig TF
mRNA levels were increased in heart xenografts compared to naive pig hearts, irrespective of
IL-6 receptor antagonist administration. Additionally, baboon TF
mRNA levels were detectable in heart xenografts, but not in naive pig hearts. Some pro-inflammatory
cytokines and
chemokines are elevated in xenograft recipients, even with efficient T cell-directed immunosuppressive therapy. Persistent elevation of D-dimers, and individual
cytokines and
chemokines suggest a continuous inflammatory response, despite administration of
anti-inflammatory agents. Systemic administration of combined
anti-inflammatory agents as well as
complement regulation may be essential to prevent SIXR after
xenotransplantation.