Introduction: Innate- and adaptive-like features of human γδ T cells are associated with different T cell receptor (TCR) repertoires, defined as Vγ9+δ2+ and non-Vγ9δ2, respectively. Immune repertoires can be shaped by tissue compartmentalization, age and history of antigen exposure. Despite comprising a significant portion of lymphocytes residing in many organs, including gut, the role of γδ T cells in transplantation outcomes is unclear.

Methods: Serial biopsies from intestinal transplantation (ITx) recipients allow us to investigate the turnover dynamics of intragraft γδ T cells in the presence and absence of rejection, providing a unique opportunity to study the fundamental biology of human γδ T cells. Clonal tracking of γδ T cells in intestinal grafts, peripheral blood and bone marrow (BM) at both pre- and post-Tx time points provides a deeper understanding of their tissue origin, migration pattern and phenotypic maturation. Integrated iRepertoire (γδ T cell primer sets) and 10x Genomics (5’cDNA library) platforms were applied to relate functional gene profiles within individual γδ T cell clonotypes.

Results: We previously demonstrated that donor T cell macrochimerism (peak level ≥4% in blood) is associated with less rejection. We now show that high levels (>10%) of γδ T cell blood chimerism were only observed in patients with macrochimerism. Remarkably, donor γδ T cells were detected in recipient BM 105–357 days post-Tx. Single-cell profiling of BM-infiltrating donor γδ T cells revealed both Vδ1- and Vδ2-dominant clonotypes with cytotoxic effector phenotypes that might contribute to graft-vs-host responses. In one multivisceral Tx patient, the top dominant donor γδ TCR clone (Vγ8Vδ1) detectable during the peak T cell chimerism in blood (8–20 days post-Tx) was also predominantly present in the recipient BM 126 days post-Tx, with clear cytotoxic profiles (GZMB/PRF1/GNLY) but reduced proliferation (MKI67) and BM-homing (CXCR4) features. BM-infiltrating donor Vδ2 clonotypes tended to be more “public” and were shared by three pediatric patient post-Tx BM specimens and pre-Tx repertoires across pediatric donors and tissues. Many of these Vδ2 clones are Vγ9δ2 with zero N-additions that likely originate from fetal liver and cord blood. However, these Vδ2-dominant clones were not present in adult lymphoid tissues, gut or BM, suggesting an age-related distribution and migration pattern. In contrast to αβ T cells, the turnover dynamics of γδ T cells in the graft showed a stronger association with donor age than with the status of macrochimerism. Graft-repopulating recipient γδ T cells showed activated effector phenotypes early post-Tx and gradually developed into cytotoxic resident-memory T cells with “private” Vδ1 clonotypes.

Conclusions: γδ T cells have the potential to modulate immune responses to influence T cell chimerism locally and systemically. They may participate in host defense and graft rejection after ITx.