Glutathione S-Transferase T1 Mismatch and Presence of Anti-GSTT1 Antibodies In Hepatic Gvhd

Abstract 2323

Graft-versus-host disease (GVHD) remains a major complication after allogenic hematopoietic stem-cell transplantation (alloHSCT) from HLA-identical donor. It is due to donor T-cell responses against minor histocompatibility antigens (mHags) of the recipient. Nevertheless, there is a complete lack of studies addressing the B-cell response to mHags in GVHD. Glutathione S-transferase T1 (GSTT1) is a drug metabolizing enzyme that is involved in detoxification processes. It is highly expressed in liver, kidney and erythrocytes. The GSTT1 gene is absent in 20% of the Caucasian population. In liver and renal transplantation, we have reported that some GSTT1-negative patients who received a GSTT1-positive graft produce anti-GSTT1 antibodies (abs) and present signs of chronic rejection. The aims of this study were to analyze the effects of GSTT1 donor/recipient mismatches in the development of hepatic GVHD and to detect production of anti-GSTT1 abs after alloHSCT. For that purpose, we have studied a group of 40 patients that received an alloHSCT from HLA-identical donors between January 2004 and July 2009 in HU Virgen del Rocío, whose DNA samples and their corresponding donor samples were available. All patients and their donors gave written informed consent. GSTT1 genotyping was performed by PCR and a commercially available ELISA test with the GSTT1 human recombinant protein was used to detect anti-GSTT1 abs. We studied abs in serum samples corresponding to different pre and post transplant phases. The distribution of the four possible GSTT1 genetic combinations was as follows: 25 donor+/recipient+, 6 donor+/recipient-, 5 donor-/recipient+ and 4 donor-/recipient-. Anti-GSTT1 antibodies were detected in 5 patients all of them with a donor that carries the null genotype. Four of the 5 patients included in the donor-/recipient+ group developed anti-GSTT1 abs (of the IgG class) after the infusion and were diagnosed with acute hepatic GVHD. In all of these cases the donor was a multiparous female. The presence of anti-GSTT1 abs is significantly associated with hepatic GVHD (p=0,01, Table 1). The fifth recipient within this group had a non-transfused male donor and did not produce abs. In all the cases, anti-GSTT1 abs were found in post-transplant serum samples of the recipient (never in pre-transplant samples) under a condition of 100% chimerism. Our hypothesis is that the immune system of the null donors has encountered the GSTT1 antigen during pregnancy of a positive-fetous and memory B-cells would be in the peripheral blood stem-cell infusion. These cells, once in a positive recipient, would be activated when contacted with the antigen present in the recipientxs liver. In the patients, the B-cells produced high levels of anti-GSTT1 abs that were associated with GVHD episodes. In conclusion, we describe that the presence of anti-GSTT1 abs is associated with the development of hepatic graft-versus-host-disease and that the null genotype of the donor is a necessary condition for antibody-production. These results confirm the GSTT1 gene as new minor histocompatibility antigen.