Friday October 11, 2019 from 17:50 to 18:30
Anti-pig IgA and IgE antibodies in the sera of naïve human and naïve and sensitized non-human primates
Hidetaka Hara1, Qi Li1, Hayato Iwase1, Takayuki Yamamoto1, David Ayares2, David K.C. Cooper1.
1Surgery, University of Alabama at Birmingham, Birmingham, AL, United States; 2Revivicor Inc., Blacksburg, VA, United States
Introduction: Natural preformed anti-pig IgM and IgG antibodies in primates play an important role in xenograft rejection. The possible roles of anti-pig IgA and IgE have not been investigated. Our aim was to measure (i) preformed serum anti-pig IgA and IgE in humans and nonhuman primates (NHPs); (ii) elicited IgA and IgE after pig organ or tissue transplantation in NHPs; (iii) their correlation with anti-pig IgM and IgG, and (iv) their deposition in rejected pig xenografts.
Methods: The binding of IgM, IgG, IgA and IgE antibodies to red blood cells (RBCs) from WT, GTKO, and TKO (i.e., not expressing Gal, Neu5Gc, or Sda xenoantigens) pigs was measured by flow cytometry in naïve humans (n=50) and baboons (n=14). Antibody binding to WT and GTKO pig (p) RBCs was also measured in the sera of baboons (non-sensitized: n=7, sensitized: n=2) and rhesus monkeys (non-sensitized: n=2, sensitized: n=11) following WT or GTKO pig organ/tissue xenotransplantation. Deposition of IgE/IgA in the grafts was detected by immunohistochemistry.
Results: (i) Humans had IgM/IgG/IgA/IgE antibodies to WT (100% in all antibody classes, relative geometric mean [RGM]: 100.4/37.5/13.6/6.3) and GTKO (100%/92%/81%/78%, RGM: 26.4/7.2/6.0/2.5) pRBCs, but no or reduced binding to TKO (8%/0%/22%/8%, RGM: 1.0/1.0/1.1/1.0) pRBCs. Mean human serum IgM binding to all type of pRBCs was greater than of IgG, IgA, and IgE (p<0.01). The levels of human serum IgA/IgE binding to TKO pRBCs were significantly lower than to WT and GTKO pRBCs (p<0.01). In naïve human sera, binding of the four classes of anti-nonGal antibodies correlated with each other (except IgG with IgA). (ii) Baboons had IgM/IgG/IgA/IgE antibodies against WT (100% in all antibody classes, RGM: 27.9/6.7/16.9/5.8) pRBCs, but less to GTKO (10%/50%/36%/14%, RGM: 2.7/1.3/1.0/1.0) and TKO (93%/50%/36%/29%, RGM: 2.7/1.1/1.2/1.0). The mean binding of both IgA and IgE to GTKO pRBCs was lower than of IgM and IgG (p<0.01). After xenotransplantation, when IgM/IgG binding to donor pRBCs increased, binding of IgA/IgE to those cells also increased (p<0.01), but to a reduced extent. There were moderate IgA and minimal IgE depositions in the pig grafts.
Conclusions: Primates, especially humans, have natural IgA/IgE antibodies to GTKO pig cells, but little or none to TKO pig cells. After exposure to a pig graft, IgA and IgE antibody levels increase, but not to the same extent as IgM or IgG. Their exact role, if any, in xenograft rejection remains uncertain.
NIAID U19 grant AI090959 .