Innate lymphoid cell recovery and occurrence of GvHD after hematopoietic stem cell transplantation.

Lymphocytes are essential for microbial immunity, tumor surveillance, and tissue homeostasis. However, the in vivo development and function of helper-like innate lymphoid cells (ILCs) in humans remain much less well understood than those of T, B, and NK cells. We monitored hematopoietic stem cell transplantation (HSCT) to determine the kinetics of ILC development in both children and adults. It was found that, unlike NK cells, helper-like ILCs recovered slowly, mirroring the pattern observed for T cells, with normalization achieved at 1 year. The type of graft and the proportion of CD34+ cells in the graft did not significantly affect ILC reconstitution. As HSCT is often complicated by acute or chronic graft-versus-host disease (GVHD), the potential role of ILC subsets in maintaining tissue integrity in these conditions was also analyzed. It was found that GVHD was associated with lower levels of activated and gut-homing NKp44+ ILCP, consistent with a non-redundant role of this ILC subset in preventing this life-threatening disorder in lymphopenic conditions.

Imbalance favoring follicular helper T cells over IL10+ regulatory B cells is detrimental for the kidney allograft.

A high frequency of regulatory B (Breg) cells, generally transitional B cells, has been associated with long-term kidney allograft survival and operational tolerance. However, circulating follicular helper T cells (cTfh) correlate with graft rejection. In order to better understand the interplay between these cell subsets and to determine their association with graft outcome we studied transitional and IL10+ Breg cells, as well as cTfh, pre- and post-transplantation in a prospective cohort of 200 kidney transplant recipients and in healthy volunteers. Patients with end-stage kidney disease had higher frequencies of transitional and IL10+ Breg cells compared to controls, and these subsets decreased during the one-year post-transplant follow-up. Higher frequencies of pre-transplant IL10+ Breg cells, and a larger reduction in these cells early post-transplantation, predicted acute rejection and graft failure. Moreover, IL10+ Breg cells correlated with cTfh pre-transplantation, and a post-transplant increase in the cTfh/IL10+Breg ratio preceded acute rejection. Thus, evaluation of pre-transplant IL10+ Breg cells and the regular monitoring of the cTfh/IL10+Breg ratio may be useful to assess post-transplant risk. Hence, our observations suggest the need to develop therapeutic strategies aimed at preserving regulatory B cells, and depleting Tfh, post-transplantation.

Donor helper innate lymphoid cells are replaced earlier than lineage positive cells and persist long-term in human intestinal grafts - a descriptive study.

Intestinal grafts carry large donor lymphoid load that is replaced by recipient cells. The dynamics of this process may influence the tolerance, rejection or graft-versus-host disease. We analysed distribution and turnover of T and B (Lin+) lymphocytes, natural killer (NK) and helper innate lymphoid cells (hILC) in intestinal epithelium (IEp) and lamina propia (LP) from a long-term cohort of eight intestinal recipients and from a single patient monitored deeply during the first 8 months post-transplant (posTx). Long-term intestinal grafts showed significantly higher %hILC than native bowels in IEp and LP until 10 years posTx and recovery to normal levels was observed afterwards. We also observed an imbalance between hILC subsets in IEp [increase of type 1 (ILC1) and decrease in type 3 (ILC3) innate lymphoid cells] that persisted along posTx time even when %hILC was similar to native bowels. Regarding hILC origin, we still detected the presence of donor cells at 13 years posTx. However, this chimerism was significantly lower than in Lin+ and NK populations. According to these findings, observation from the patient monitored in early posTx period showed that recipient hILC repopulate earlier and faster than Lin+ cells, with increase in ILC1 related to rejection and infection episodes.

Number and function of circulatory helper innate lymphoid cells are unaffected by immunosuppressive drugs used in solid organ recipients - a single centre cohort study.

In transplanted intestines, depletion of T cells together with long-term persistence of ILC is observed, suggesting ILC insensitivity to immunosuppressive drugs. To further analyze helper ILC (hILC) apparent resistance to therapy, cytotoxic ILC (NK cells), hILC subsets (ILC1, ILC2, and ILC precursors (ILCP)), and their signature cytokines (IFNγ, IL4 + IL13, and IL22) were analyzed in peripheral blood of kidney and liver transplant recipients. Early after transplantation (posTx), transplanted patients showed significantly lower Lin + and NK cells, whereas total hILC, ILC1, ILC2, and ILCP numbers were similar in patients and controls. Between paired pre- and posTx samples, Lin + cell and NK cell counts significantly decreased, whereas all three hILC counts and their cytokine production remained similar. ILC1, ILC2, and ILCP numbers were also similar in patients under thymoglobulin or basiliximab (BAS), patients without induction (only maintenance therapy) and controls. hILC showed lower TMG binding comparing to Lin + cells, reduced expression of CD25 (BAS target), and diminished calcineurin activity with undetectable calcineurin and FKBP12 (tacrolimus target). hILC counts were not related to delayed graft function or biopsy-proven acute rejection. Thus, hILC remain stable early after transplantation and seem unaffected by immunosuppressors, which may be related to reduced targets expression and low calcineurin activity.

Longitudinal profile of circulating T follicular helper lymphocytes parallels anti-HLA sensitization in renal transplant recipients.

Antibody-mediated rejection is responsible for 30%-50% of renal graft failures. Differentiation of B cells into antibody-producing plasmablasts depends on the collaboration of follicular helper T cells (Tfh). We analyzed circulating Tfh (cTfh) in kidney recipients and studied cTfh relationship with anti-HLA antibody production and graft outcome. cTfh were longitudinally analyzed in a prospective cohort of patients (n = 206), pre- and posttransplantation. Clinical data, HLA sensitization, and cTfh function were recorded. Both pretransplant and 6-month posttransplant cTfh were able to derive IgG-producing plasmablasts. Pretransplant cTfh was decreased in patients, especially in those who received dialysis. However, these cells were increased in patients with previous allograft or transfusions and in HLA-sensitized recipients. After transplantation cTfh expanded, significantly more in patients who developed de novo anti-HLA antibodies than in patients who remained unsensitized. Augmented pretransplant cTfh positively correlated with higher intensity of pretransplant anti-HLA class I and with de novo anti-HLA class I and anti-HLA class II antibodies. Consistently, pretransplantation cTfh were higher in patients who experienced acute rejection (HR = 1.14 [1.04-1.25]). Thus, we show a role for Tfh in anti-HLA sensitization and rejection. Multicenter studies with additional patient cohorts are needed to validate these results. Immunosuppressive drugs targeting Tfh could be useful to improve outcomes.

Donor-Specific Antibodies in Pediatric Intestinal and Multivisceral Transplantation: The Role of Liver and Human Leukocyte Antigen Mismatching.

Rejection is one of the most important drawbacks for graft and patient survival in intestinal and multivisceral transplantation. However, there is no consensus on the diagnostic criteria for humoral rejection, and the literature about the role of donor-specific antibodies (DSA) on allograft outcome and the risk factors that contribute to their development is scant with contradictory results. The present study analyzes the role of DSA exclusively in a pediatric cohort of 43 transplants. Among our patients, 11.6% showed preformed DSA, but they did not correlate with more rejection or less allograft survival. Having previous transplants was the main sensitization factor with an odds ratio (OR) = 44.85 (P = 0.001). In total, 16.3% of recipients developed de novo donor-specific antibodies (dnDSA), mostly directed against human leukocyte antigen (HLA) class II, polyspecific and complement fixing. Additionally, the presence of dnDSA had a deleterious effect on graft rejection (hazard ratio [HR] = 11.00; P = 0.01) and survival (HR = 66.52; P < 0.001) in an observational period of 5 years after transplantation. The inclusion of the liver emerged as the main protective factor against dnDSA development with an OR = 0.07 (P = 0.007). The analysis of HLA compatibility at the serological and epitope level with the computational tools HLAMatchmaker and PIRCHE revealed no association between HLA mismatching and dnDSA. In conclusion, this study performed in pediatric recipients shows the deleterious effect of dnDSA on intestinal transplantation supported by the complement-fixing activity observed. Additionally, the liver inclusion in the allografts showed to be a protective factor against dnDSA generation.