Why do some females reject males? The molecular basis for male-specific graft rejection

Distinct sets of molecular characteristics define tumor-rejecting neoantigens

Challenges in identifying tumor-rejecting neoantigens limit the efficacy of neoantigen vaccines to treat cancers, including cutaneous squamous cell carcinoma (cSCC). A minority of human cSCC tumors shared neoantigens, supporting the need for personalized vaccines. Using a UV-induced mouse cSCC model which recapitulated the mutational signature and driver mutations found in human disease, we found that CD8 T cells constrain cSCC. Two MHC class I neoantigens were identified that constrained cSCC growth. Compared to the wild-type peptides, one tumor-rejecting neoantigen exhibited improved MHC binding and the other had increased solvent accessibility of the mutated residue. Across known neoantigens that do not impact MHC binding, structural modeling of the peptide/MHC complexes indicated that increased solvent accessibility, which will facilitate TCR recognition of the neoantigen, distinguished tumor-rejecting from non-immunogenic neoantigens. This work reveals characteristics of tumor-rejecting neoantigens that may be of considerable importance in identifying optimal vaccine candidates in cSCC and other cancers.

The role of donor-recipient gender matching in lung transplantation: a systematic review

INTRODUCTION

Donor to recipient (D-R) matching in lung transplantation (LTx) is firstly directed by blood group (identity or compatibility), immunological status and morphological criteria. Sex matching is ignored and impact on outcome less investigated.

EVIDENCE ACQUISITION

Systematic review of English literature using PubMed (1990-2019) was performed to evaluate the potential role of D-R matching in determining long-term outcome in patients after LTx. Search terms included (LTx) AND (sex) OR (gender) OR (matching) OR (mismatch) OR (donor characteristics) and were restricted to articles' title. Only articles directly reporting LTx survival outcome according to gender match/mismatch and D-R gender combination in LTx were included. Two authors independently extracted articles using predefined data fields, including study quality indicators. MOOSE Guidelines for Meta-Analyses and Systematic Reviews of Observational Studies applied.

EVIDENCE SYNTHESIS

Nine articles were analyzed and included into this study. All studies analyzed the effect of the different D-R gender combinations on survival while seven of them investigated exclusively the role of sex matching on LTx outcome. In this latter group two out of seven showed a trend towards an overall survival advantage for sex matching LTx combination. The worst survival results were reported for F to M gender combination in 3 studies and for M to F gender combination by 1 study. No differences were reported in remaining 4 studies.

CONCLUSIONS

This systematic review suggests that sex matching and several gender combinations could play a role in determining overall survival rate after LTx. Data deriving from unbiased studies supported that matching female-female (F-F) and male-male (M-M) could improve LTx outcome while FD-MR combination should be avoided. Unfortunately, a good part of the analyzed data are affected by bias due to confounding factors. Up-to-date immunological, hormonal and morphological factors could explain the gender-based difference in LTx outcome. Further investigations should clarify their role and importance to define the effects of gender combinations on survival.

Association of Sex Mismatch Between Donor and Recipient With Graft Survivorship at 5 Years After Osteochondral Allograft Transplantation

BACKGROUND

Sex mismatch between donor and recipient has been considered a potential contributor to adverse outcomes after solid organ transplantation. However, the influence of sex mismatching in osteochondral allograft (OCA) transplantation has yet to be determined.

PURPOSE

To evaluate whether donor-recipient sex mismatching affects graft survival after OCA transplantation.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

In this review of prospectively collected data, patients who underwent OCA transplantation between November 2013 and November 2017 by a single surgeon were analyzed. Cumulative survival was assessed via the Kaplan-Meier method using log-rank tests to compare patients with similar donor groups. Multivariable Cox regression analysis adjusted for patient age, graft size, and body mass index was used to evaluate the influence of donor-recipient sex on graft survival.

RESULTS

A total of 154 patients were included: 102 (66.2%) who received OCAs from a same-sex donor and 52 (33.8%) who received OCAs from a different-sex donor. At 5-year follow-up, a significantly lower graft survival rate was observed for different-sex donor transplantation in comparison with same-sex donorship (63% vs 92%; P = .01). When correcting for age, graft size, and body mass index, donor-recipient sex-mismatch transplantation demonstrated a 2.9-times greater likelihood to fail at 5 years compared with donor-recipient same-sex transplantation (95% CI, 1.11-7.44; P = .03). A subgroup analysis showed no significant difference in graft survival between the female-to-female and female-to-male groups (91% and 84%, respectively). Conversely, male-to-male transplantation demonstrated a significantly higher cumulative 5-year survival (94%; P = .04), whereas lower survival was found with male-to-female donorship (64%; P = .04). Multivariable Cox regression indicated a 2.6-times higher likelihood of failure for the male-to-female group in comparison with the other groups (95% CI, 1.03-6.69; P = .04). Male-to-male transplantation had a tendency toward decreased likelihood of OCA failure (hazard ratio, 0.33), although without statistical significance (95% CI, 0.11-1.01; P = .052).

CONCLUSION

Mismatch between donor and recipient sex had a negative effect on OCA survival after transplantation, particularly in those cases when male donor tissue was transplanted into a female recipient.

High Levels of Copy Number Variation of Ampliconic Genes across Major Human Y Haplogroups

Because of its highly repetitive nature, the human male-specific Y chromosome remains understudied. It is important to investigate variation on the Y chromosome to understand its evolution and contribution to phenotypic variation, including infertility. Approximately 20% of the human Y chromosome consists of ampliconic regions which include nine multi-copy gene families. These gene families are expressed exclusively in testes and usually implicated in spermatogenesis. Here, to gain a better understanding of the role of the Y chromosome in human evolution and in determining sexually dimorphic traits, we studied ampliconic gene copy number variation in 100 males representing ten major Y haplogroups world-wide. Copy number was estimated with droplet digital PCR. In contrast to low nucleotide diversity observed on the Y in previous studies, here we show that ampliconic gene copy number diversity is very high. A total of 98 copy-number-based haplotypes were observed among 100 individuals, and haplotypes were sometimes shared by males from very different haplogroups, suggesting homoplasies. The resulting haplotypes did not cluster according to major Y haplogroups. Overall, only two gene families (RBMY and TSPY) showed significant differences in copy number among major Y haplogroups, and the haplogroup of a male could not be predicted based on his ampliconic gene copy numbers. Finally, we did not find significant correlations either between copy number variation and individual's height, or between the former and facial masculinity/femininity. Our results suggest rapid evolution of ampliconic gene copy numbers on the human Y, and we discuss its causes.

Donor-Specific Antibodies in Kidney Transplant Recipients

Donor-specific antibodies have become an established biomarker predicting antibody-mediated rejection. Antibody-mediated rejection is the leading cause of graft loss after kidney transplant. There are several phenotypes of antibody-mediated rejection along post-transplant course that are determined by the timing and extent of humoral response and the various characteristics of donor-specific antibodies, such as antigen classes, specificity, antibody strength, IgG subclasses, and complement binding capacity. Preformed donor-specific antibodies in sensitized patients can trigger hyperacute rejection, accelerated acute rejection, and early acute antibody-mediated rejection. De novo donor-specific antibodies are associated with late acute antibody-mediated rejection, chronic antibody-mediated rejection, and transplant glomerulopathy. The pathogeneses of antibody-mediated rejection include not only complement-dependent cytotoxicity, but also complement-independent pathways of antibody-mediated cellular cytotoxicity and direct endothelial activation and proliferation. The novel assay for complement binding capacity has improved our ability to predict antibody-mediated rejection phenotypes. C1q binding donor-specific antibodies are closely associated with acute antibody-mediated rejection, more severe graft injuries, and early graft failure, whereas C1q nonbinding donor-specific antibodies correlate with subclinical or chronic antibody-mediated rejection and late graft loss. IgG subclasses have various abilities to activate complement and recruit effector cells through the Fc receptor. Complement binding IgG3 donor-specific antibodies are frequently associated with acute antibody-mediated rejection and severe graft injury, whereas noncomplement binding IgG4 donor-specific antibodies are more correlated with subclinical or chronic antibody-mediated rejection and transplant glomerulopathy. Our in-depth knowledge of complex characteristics of donor-specific antibodies can stratify the patient's immunologic risk, can predict distinct phenotypes of antibody-mediated rejection, and hopefully, will guide our clinical practice to improve the transplant outcomes.

The impact of donor and recipient weight incompatibility on renal transplant outcomes

BACKGROUND

Donor/recipient size mismatching and correlation to allograft outcome remains poorly defined. This study assessed the impact of donor body weight (DBW) to recipient body weight (RBW) ratio on allograft function and survival.

METHODS

A total of 898 deceased donor renal transplant recipients were included in the study. Patients were divided into quartiles depending on the ratio of DBW/RBW: Q1 (≤ 0.88), Q2 (0.89-1.00), Q3 (1.01-1.22) and Q4 (> 1.22). Donor and recipient characteristics were obtained from the national kidney transplant service database. Serum creatinine and estimated glomerular filtration rate (eGFR) at 1 and 5 years after transplant were compared.

RESULTS

Q4 patients had a higher eGFR 1 year post-transplant (median 59.5 ml/min, IQR 46.8-76.2) compared to Q1-Q3 which had median eGFRs of 54.3, 54.8 and 55.3 ml/min, respectively (p < 0.001). At 5 years post-transplant, there were modest differences in the eGFR across the four quartiles, Q1-4 with median eGFRs of 56.9, 61.1, 61.2 and 58.6 ml/min, respectively (p = 0.02). However, there were no significant differences in 1- and 5-year allograft survival between groups.

CONCLUSIONS

In the setting of deceased donor renal transplantation, mismatching of donor to recipient weight had no impact on 5-year allograft survival, but a low DBW/RBW ratio is modestly associated with lower eGFR.

Organ transplantation and gender differences: a paradigmatic example of intertwining between biological and sociocultural determinants

Organ transplantation, e.g., of the heart, liver, or kidney, is nowadays a routine strategy to counteract several lethal human pathologies. From literature data and from data obtained in Italy, a striking scenario appears well evident: women are more often donors than recipients. On the other hand, recipients of organs are mainly males, probably reflecting a gender bias in the incidence of transplant-related pathologies. The impact of sex mismatch on transplant outcome remains debated, even though donor-recipient sex mismatch, due to biological matters, appears undesirable in female recipients. In our opinion, the analysis of how sex and gender can interact and affect grafting success could represent a mandatory task for the management of organ transplantation.

Minor Antigen Vaccine-Sensitized DLI: In Vitro Responses Do Not Predict In Vivo Effects

Background

We reported on a pilot study of minor histocompatibility antigen vaccination using constructs expressing male-specific gene disparities of selected mouse CDNA on Y and sex determining region Y in the canine model. We performed reduced-intensity hematopoietic cell transplantation with female donors and male recipients, producing stable mixed donor-recipient hematopoietic chimeras. We then performed a vaccine series in three female transplant donors followed by donor lymphocyte infusion (DLI) into their respective mixed chimeras. One mixed chimera experienced a significant shift in the percentage of donor chimerism, but no response occurred in the other 2 recipients. We then hypothesized that inadequate donor sensitization was responsible for these results.

Methods

To test this hypothesis, we added 4 monthly booster vaccinations to 2 of the original hematopoietic cell transplantation donors, including the donor that drove the partial response, followed by a second DLI.

Results

Strong T cell responses were shown by ELISpot and confirmed by intracellular cytokine staining in both donors. A second DLI resulted in a further increase in donor chimerism in the same mixed chimera that experienced the previous increase, but no change in donor chimerism was again seen in the other recipient. Evaluation of RNA expression of the target antigens demonstrated that conversion occurred in the recipient that expressed both selected mouse CDNA on Y and sex determining region Y.

Conclusions

T cell responses against Y chromosome-encoded disparities were not necessarily sufficient to drive in vivo female antimale responses. Other factors including the presence of specific haplotypes or the heterogeneous expression of the target antigen may affect T cell responses against minor histocompatibility antigens. These results warrant future vaccine studies in a larger transplant cohort using epigenetic modulation of the recipient to promote target gene expression.

Essential concept of transplant immunology for clinical practice

Our understanding of transplant immunology has advanced from gross allograft rejection to cellular response and to current molecular level. More sensitive assays have been developed to characterize patient sensitization and to detect pre-existing donor-specific antibodies (DSA) in pre-transplant crossmatch. After a transplant, pre-existing or de novo DSA are increasingly monitored to guide clinical management. Therefore, it is important for clinicians to understand the basic concepts and key components of transplant immunology as well as be familiarized with the modern immunological techniques used in kidney transplantation.

Deletion of naïve T cells recognizing the minor histocompatibility antigen HY with toxin-coupled peptide-MHC class I tetramers inhibits cognate CTL responses and alters immunodominance

Alloreactive T-cell responses directed against minor histocompatibility (H) antigens, which arise from diverse genetic disparities between donor and recipient outside the MHC, are an important cause of rejection of MHC-matched grafts. Because clinically significant responses appear to be directed at only a few antigens, the selective deletion of naïve T cells recognizing donor-specific, immunodominant minor H antigens in recipients before transplantation may be a useful tolerogenic strategy. We have previously demonstrated that peptide-MHC class I tetramers coupled to a toxin can efficiently eliminate specific TCR-transgenic T cells in vivo. Here, using the minor histocompatibility antigen HY as a model, we investigated whether toxic tetramers could inhibit the subsequent priming of the two H2-D(b)-restricted, immunodominant T-cell responses by deleting precursor CTL. Immunization of female mice with male bone marrow elicited robust CTL activity against the Uty and Smcy epitopes, with Uty constituting the major response. As hypothesized, toxic tetramer administration prior to immunization increased survival of cognate peptide-pulsed cells in an in vivo CTL assay, and reduced the frequency of corresponding T cells. However, tetramer-mediated decreases in either T-cell population magnified CTL responses against the non-targeted epitope, suggesting that D(b)-Uty(+) and D(b)-Smcy(+) T cells compete for a limited common resource during priming. Toxic tetramers conceivably could be used in combination to dissect manipulate CD8(+) T-cell immunodominance hierarchies, and to prevent the induction of donor-specific, minor H antigen CTL responses in allotransplantation.

Mouse models for graft arteriosclerosis

Graft arteriosclerois (GA), also called allograft vasculopathy, is a pathologic lesion that develops over months to years in transplanted organs characterized by diffuse, circumferential stenosis of the entire graft vascular tree. The most critical component of GA pathogenesis is the proliferation of smooth muscle-like cells within the intima. When a human coronary artery segment is interposed into the infra-renal aortae of immunodeficient mice, the intimas could be expand in response to adoptively transferred human T cells allogeneic to the artery donor or exogenous human IFN-γ in the absence of human T cells. Interposition of a mouse aorta from one strain into another mouse strain recipient is limited as a model for chronic rejection in humans because the acute cell-mediated rejection response in this mouse model completely eliminates all donor-derived vascular cells from the graft within two-three weeks. We have recently developed two new mouse models to circumvent these problems. The first model involves interposition of a vessel segment from a male mouse into a female recipient of the same inbred strain (C57BL/6J). Graft rejection in this case is directed only against minor histocompatibility antigens encoded by the Y chromosome (present in the male but not the female) and the rejection response that ensues is sufficiently indolent to preserve donor-derived smooth muscle cells for several weeks. The second model involves interposing an artery segment from a wild type C57BL/6J mouse donor into a host mouse of the same strain and gender that lacks the receptor for IFN-γ followed by administration of mouse IFN-γ (delivered via infection of the mouse liver with an adenoviral vector. There is no rejection in this case as both donor and recipient mice are of the same strain and gender but donor smooth muscle cells proliferate in response to the cytokine while host-derived cells, lacking receptor for this cytokine, are unresponsive. By backcrossing additional genetic changes into the vessel donor, both models can be used to assess the effect of specific genes on GA progression. Here, we describe detailed protocols for our mouse GA models.

Gene expression profiling of allogeneic islet grafts in an experimental mouse model before rejection or tolerance phenotypes arise

BACKGROUND

It has been reported that an HY antigen-mismatched islet transplantation can induce peripheral tolerance. However, the factors that initiate the peripheral tolerance are not clear. This study was designed to examine which genes were most important for the induction of peripheral tolerance.

METHODS

Islets from female Balb/c and male C57BL/6 mice were transplanted underneath the left perirenal capsule of female C57BL/6 recipient mice rendered diabetic by intraperitoneal injection of streptozotocin. Before rejection or tolerance phenotypes arose, we harvested islet grafts for cDNA microarray analysis.

RESULTS

Minor antigen-mismatched islets transplanted into recipient mice showed no rejection or tolerance phenotypes until 12 days posttransplantation. When we confirmed, decreased functional islet grafts and increased inflammatory cell infiltration. Gene expression profiles revealed differences in expression among groups. Major histocompatibility complex-mismatched islets induced upregulation of 209 genes and downregulation of 10 genes compared with the HY antigen-mismatched islet (2-fold; P < .05). Of these, 3 genes exhibited significant changes in expression levels in Balb/c donor islet grafts compared with C57BL/6 donor islet grafts: Gad1, Gdf10, and Scg2 (P < .01).

CONCLUSIONS

The present study suggested that 3 genes showed a significant relationship to protection against graft rejection. The identification of these genes may help to understand signaling pathways, involved in the communication between transplanted islet grafts and recipients in vivo.

AIP1 in graft arteriosclerosis

Graft arteriosclerosis (GA), the major cause of late cardiac allograft failure, is characterized by a diffuse, concentric arterial intimal hyperplasia composed of infiltrating host T cells, macrophages, and predominantly graft-derived smooth muscle-like cells that proliferate and elaborate extracellular matrix, resulting in luminal obstruction and allograft ischemia. Interferon-γ (IFN-γ), a proinflammatory cytokine produced by effector T cells, is a critical mediator for smooth muscle-like cell proliferation. We have exploited the power of mouse genetics to examine the function of AIP1, a signaling adaptor molecule involved in vascular inflammation, in two newly established IFN-γ-mediated models of GA. Our data suggest that AIP1 inhibits intimal formation in GA by downregulating IFN-γ-activated migratory and proliferative signaling pathways in smooth muscle-like cells.

H-Y Antigen Incompatibility Not Associated with Adverse Immunologic Graft Outcomes: Deceased Donor Pair Analysis of the OPTN Database

Background. H-Y antigen incompatibility adversely impacts bone marrow transplants however, the relevance of these antigens in kidney transplantation is uncertain. Three previous retrospective studies of kidney transplant databases have produced conflicting results. Methods. This study analyzed the Organ Procurement and Transplantation Network database between 1997 and 2009 using male deceased donor kidney transplant pairs in which the recipient genders were discordant. Death censored graft survival at six months, five, and ten years, treated acute rejection at six months and one year, and rates of graft failure by cause were the primary endpoints analyzed. Results. Death censored graft survival at six months was significantly worse for female recipients. Analysis of the causes of graft failure at six months revealed that the difference in death censored graft survival was due primarily to nonimmunologic graft failures. The adjusted and unadjusted death censored graft survivals at five and ten years were similar between the two genders as were the rates of immunologic graft failure. No difference in the rates of treated acute rejection at six months and one year was seen between the two genders. Conclusions. Male donor to female recipient discordance had no discernable effect on immunologically mediated kidney graft outcomes in the era of modern immunosuppression.

AIP1 prevents graft arteriosclerosis by inhibiting interferon-γ-dependent smooth muscle cell proliferation and intimal expansion

RATIONALE

ASK1-interacting protein-1 (AIP1), a Ras GTPase-activating protein family member, is highly expressed in endothelial cells and vascular smooth musccells (VSMCs). The role of AIP1 in VSMCs and VSMC proliferative disease is not known.

OBJECTIVE

We used mouse graft arteriosclerosis models characterized by VSMC accumulation and intimal expansion to determine the function of AIP1.

METHODS AND RESULTS

In a single minor histocompatibility antigen (male to female)-dependent aorta transplantation model, AIP1 deletion in the graft augmented neointima formation, an effect reversed in AIP1/interferon-γ receptor (IFN-γR) doubly-deficient aorta donors. In a syngeneic aortic transplantation model in which wild-type or AIP1-knockout mouse aortas were transplanted into IFN-γR-deficient recipients and in which neointima formation was induced by intravenous administration of an adenovirus that encoded a mouse IFN-γ transgene, donor grafts from AIP1-knockout mice enhanced IFN-γ-induced VSMC proliferation and neointima formation. Mechanistically, knockout or knockdown of AIP1 in VSMCs significantly enhanced IFN-γ-induced JAK-STAT signaling and IFN-γ-dependent VSMC migration and proliferation, 2 critical steps in neointima formation. Furthermore, AIP1 specifically bound to JAK2 and inhibited its activity.

CONCLUSIONS

AIP1 functions as a negative regulator in IFN-γ-induced intimal formation, in part by downregulating IFN-γ-JAK2-STAT1/3-dependent migratory and proliferative signaling in VSMCs.

Fetal derived embryonic-like stem cells improve healing in a large animal flexor tendonitis model

Introduction

Tendon injury is a common problem in athletes, with poor tissue regeneration and a high rate of re-injury. Stem cell therapy is an attractive treatment modality as it may induce tissue regeneration rather than tissue repair. Currently, there are no reports on the use of pluripotent cells in a large animal tendon model in vivo. We report the use of intra-lesional injection of male, fetal derived embryonic-like stem cells (fdESC) that express Oct-4, Nanog, SSEA4, Tra 1-60, Tra 1-81 and telomerase.

Methods

Tendon injury was induced using a collagenase gel-physical defect model in the mid-metacarpal region of the superficial digital flexor tendon (SDFT) of eight female adult Thoroughbred or Thoroughbred cross horses. Tendon lesions were treated one week later with intra-lesional injection of male derived fdESCs in media or media alone. Therapy was blinded and randomized. Serial ultrasound examinations were performed and final analysis at eight weeks included magnetic resonance imaging (MRI), biochemical assays (total DNA, glycosaminoglycan, collagen), gene expression (TNC, TNMD, SCX, COL1A1, COL3A1, COMP, DCN, MMP1, MMP3, MMP13, 18S) and histology. Differences between groups were assessed with Wilcoxon's rank sum test.

Results

Cell survival was demonstrated via the presence of the SRY gene in fdESC treated, but not control treated, female SDFT at the end of the trial. There were no differences in tendon matrix specific gene expression or total proteoglycan, collagen or DNA of tendon lesions between groups. Tissue architecture, tendon size, tendon lesion size, and tendon linear fiber pattern were significantly improved on histologic sections and ultrasound in the fdESC treated tendons.

Conclusions

Such profound structural effects lend further support to the notion that pluripotent stem cells can effect musculoskeletal regeneration, rather than repair, even without in vitro lineage specific differentiation. Further investigation into the safety of pluripotent cellular therapy as well as the mechanisms by which repair was improved seem warranted.

Assessment of graft function in rodent models of heart transplantation

Heterotopic heart transplantation in rats and mice is the most commonly used model to study allograft immune response and to test immunosuppressive drugs and tolerance induction protocols. Standardization of both the surgical procedure and the evaluation of graft function is essential for data interpretation. The most popular way to monitor graft function has been the palpation method. However, there are some proposal for more objective assessment methods like electrocardiogram and echocardiogram. Although, complementary tests might add some relevant information when assessing minor effects of immunosuppressive therapy, palpation by an experienced investigator is very predictive and so far the simplest method to determine heart allograft function. Minor complications during the surgical procedure and unreliable assessment can have a major impact on the interpretation of experiment results. Here, the author reviews the literature and presents some suggestions that help eliminating biases on the assessment of heart allograft function.

Antigen loading of DCs with irradiated apoptotic tumor cells induces improved anti-tumor immunity compared to other approaches

Dendritic cells (DCs) serve as central regulators of adaptive immunity by presenting antigens and providing necessary co-signals. Environmental information received by the DCs determines the co-signals delivered to the responding adaptive cells and, ultimately, the outcome of the interaction. DCs loaded with relevant antigens have been used as therapeutic cellular vaccines, but the optimal antigen loading method has not been determined. We compared different methods to load class I and class II epitopes from the male antigenic complex, HY, onto DCs for the potency of the immune response induced in vivo. Co-incubation of female DCs with HY peptides, RNA or cell lysate from HY expressing tumor induced immune responses equivalent to male DCs. In contrast, female DCs incubated with irradiated, apoptotic HY expressing tumor cells (or male B cells) generated a stronger immune response than male DCs or female DCs loaded using any of the other methods. DC loading with apoptotic tumor resulted in complete protection against high dose HY-expressing tumor challenge whereas 100% lethality was observed in groups receiving DCs that were loaded with peptides, RNA, or lysate. We conclude that signals provided to the DCs by apoptotic cells substantially augment the potency of DC vaccines.

HA-1 Mismatch Has Significant Effect in Chronic Allograft Nephropathy in Clinical Renal Transplantation

BACKGROUND

The minor histocompatibility antigen HA-1 occurs in two allelic forms: H and R. The HA-1(H) form presented in the context of HLA A2 can elicit specific cytotoxic lymphocyte (CTL) responses and can cause graft-versus-host disease in marrow transplants. However, its significance in solid organ transplants is unknown. We determined whether incompatibility of the HA-1 resulted in enhanced rejection and whether HA-1 specific CTLs were generated.

MATERIALS AND METHODS

HLA A2-matched donor/recipient pairs were selected and typed for HA-1 antigens by polymerase chain reaction. Nineteen of 81 pairs were mismatched for HA-1. Peripheral blood mononuclear leucocytes from five recipients, HLA A2 DR-matched with donors, were stimulated for 3 days with third-party donor, matched for HLA A2 DR but mismatched for HA-1. Cells were stained for surface markers, HA-1(H)-specific tetramer reagent, and analyzed by flow cytometry. Controls were unstimulated cells; PBML from two patients never exposed to HA-1(H); immunoglobulin G isotype-matched controls. For all patients, acute rejection rates posttransplant was ascertained. Long-term data was available for 36 patients.

RESULTS AND CONCLUSIONS

There was no difference in acute rejection rates between the HA-1-matched and -mismatched groups, but there was a significant difference in chronic rejection rates, evidenced by increased graft failures during the follow-up period (P = .0024). Lymphocytes from five HA-1-mismatched recipients were stimulated in vitro with cells from HLA-A2 and DR-matched but HA-1-mismatched surrogate donor. Though there seemed to be an excess of tetramer-positive cells, anti-HA-1-specific CTL responses were not conclusively elicited in vitro.

Glial grafting for demyelinating disease

Remyelination of demyelinated central nervous system (CNS) axons is considered as a potential treatment for multiple sclerosis, and it has been achieved in experimental models of demyelination by transplantation of pro-myelinating cells. However, the experiments undertaken have not addressed the need for tissue-type matching in order to achieve graft-mediated remyelination since they were performed in conditions in which the chance for graft rejection was minimized. This article focuses on the factors determining survival of allogeneic oligodendrocyte lineage cells and their contribution to the remyelination of demyelinating CNS lesions. The immune status of the CNS as well as the suitability of different models of demyelination for graft rejection studies are discussed, and ways of enhancing allogeneic oligodendrocyte-mediated remyelination are presented. Finally, the effects of glial graft rejection on host remyelination are described, highlighting the potential benefits of the acute CNS inflammatory response for myelin repair.

CD8 T Cells Specific for a Donor-Derived, Self-Restricted Transplant Antigen Are Nonpathogenic Bystanders after Vascularized Heart Transplantation in Mice

CD8 T cell cross-priming, an established mechanism of protective antiviral immunity, was originally discovered during studies involving minor transplantation Ags. It is unclear whether or how cross-primed CD8 T cells, reactive to donor-derived, but recipient class I MHC-restricted epitopes, could injure a fully MHC-disparate, vascularized transplant. To address this question we studied host class I MHC-restricted, male transplantation Ag-reactive T cell responses in female recipients of fully MHC-disparate, male heart transplants. Cross-priming to the immune-dominant determinant HYUtyp occurred at low frequency after heart transplantation. CD8 T cell preactivation through immunization with HYUtyp mixed in CFA did not alter the kinetics of acute rejection. Furthermore, neither HYUtyp immunization nor adoptive transfer of HYUtyp-specific TCR-transgenic T cells affected outcome in 1) a model of chronic rejection in the absence of immunosuppression or 2) a model of allograft acceptance induced by costimulatory blockade. The results support the contention that CD8 T cells reactive to host-restricted, but donor-derived, Ags are highly specific and are nonpathogenic bystanders during rejection of MHC-disparate cardiac allografts.

Quantitative analysis of survival of transplanted smooth muscle cells with real-time polymerase chain reaction

BACKGROUND

Cell transplantation improves heart function after myocardial infarction. This study investigated the survival of implanted cells in normal and infarcted myocardium.

METHODS

Male rat aortic smooth muscle cells were cultured. For the in vitro study, male smooth muscle cells mixed with female smooth muscle cells or male smooth muscle cells injected into a piece of female rat myocardium were used to evaluate the accuracy of quantitative real-time polymerase chain reaction to measure Y chromosomes. For the in vivo study, 2 million live or dead male smooth muscle cells were injected into normal or infarcted female myocardium. At 1 hour and 1 and 4 weeks after transplantation, hearts, lungs, and kidneys were harvested for measurement of Y chromosomes.

RESULTS

In vitro, the accuracy of polymerase chain reaction measurement was excellent in cultured cells (r2 = 0.996) and the myocardium (r2 = 0.786). In vivo, 1 hour after 2 x 10(6) cell implantation, live cell numbers decreased to 1.0 +/- 0.2 x 10 6 and 1.1 +/- 0.3 x 10(6) , and dead cell numbers decreased to 0.9 +/- 0.2 x 10(6) and 0.8 +/- 0.2 x 10(6) in the normal and infarcted myocardium, respectively (P < .01 for all groups). Lungs and kidneys contained 8.5% and 1.5% of the implanted cells, but no cells were detected at 1 week. At 1 week, no dead smooth muscle cells were detected in the normal or infarcted myocardium. The numbers of live cells at 1 and 4 weeks were 0.48 +/- 0.06 x 10(6) and 0.27 +/- 0.07 x 10(6) in normal myocardium and 0.29 +/- 0.08 x 10(6) and 0.18 +/- 0.05 x 10(6) in infarcted myocardium.

CONCLUSIONS

One hour after implantation, only 50% of smooth muscle cells remained in the implanted area. Some implanted cells deposited in other tissue. Implanted cell survival progressively decreased during the 4-week study.

UTY-specific TCR-transfer generates potential graft-versus-leukaemia effector T cells

Immunotherapeutic approaches that target antigens that are differentially recognized on haematopoietic and non-haematopoietic cells may specifically enhance the graft-versus-leukaemia (GVL) effect of donor lymphocyte infusion. In this study, we have characterized a new HLA-B*5201-restricted epitope of the UTY gene. Unusually, presentation of this epitope was restricted to lymphoblasts. As a result, a T cell clone specific to this epitope recognized normal and malignant male B and T lymphoblasts, while showing little reactivity towards male HLA-B*5201+ fibroblasts. Transfer of its T cell receptor (TCR) into donor T cells led to the generation of large numbers of T cells, which acquired the specificity of the original clone, its avidity and the differential pattern of reactivity towards lymphoblasts and fibroblasts. Remarkably, the specific response of TCR-transferred T cells was significantly higher than that of the original clone. This is the first demonstration of the possibility to preserve the specific pattern of a T cell response to a differentially expressed antigen after TCR-transfer and to augment the amplitude of this response concomitantly. These results indicate that it may be feasible to enhance the GVL effect of donor lymphocyte infusions in lymphoproliferative malignancies by the transfer of TCRs specific to epitopes that are differentially recognized on lymphoblasts.

T-cell allorecognition and transplant rejection: a summary and update

Transplant biologists have made significant progress over the last 20 years towards unraveling the immunologic intricacies of allograft rejection. This large body of work has resulted in an improved understanding of T-cell allorecognition at a molecular level and has provided new insight into the functional consequences resulting from the allorecognition events. The findings suggest that the survival and the histologic features of a transplanted organ are influenced not only by the T-cell recognition pathway, but also by the frequency, the induced effector functions and the specific cellular targets of the alloreactive T-cell repertoire.

Prevention of acute graft-versus-host-disease by selective depletion of T cells reactive with minor histocompatibility antigens on epithelial cells

Graft-versus-host disease (GVHD) is a major obstacle in allogeneic hematopoietic stem cell transplantation (HSCT). Mature donor T-cells present in the graft play a pivotal role in the development of acute GVHD. On the other hand, mature donor T-cells in the graft are also crucial for the elimination of residual tumor cells still present in the patient after HSCT. Whether donor T cells act non-specifically against the patient, including an overlapping GVHD/GVL reactivity, or some donor T cells have GVHD reactivity while other donor T cells have GVL reactivity is still unclear. Some in-vitro data are suggestive that selective T cell depletion techniques are possible by which GVHD-reactive T cells can be eliminated while GVL-reactive T cells are preserved. Here we update some approaches of selective T cell depletion that have been developed in our laboratory.

Do X and Y spermatozoa differ in proteins?

This article reviews the current knowledge about X- and Y-chromosomal gene expression during spermatogenesis and possible differences between X- and Y-chromosome-bearing spermatozoa (X and Y sperm) in relation to whether an immunological method of separation of X and Y spermatozoa might some day be feasible. Recent studies demonstrated that X- and Y-chromosome-bearing spermatids do express X- and Y-chromosomal genes that might theoretically result in protein differences between X and Y sperm. Most, if not all, of these gene products, however, are expected to be shared among X and Y spermatids via intercellular bridges. Studies on aberrant mouse strains indicate that complete sharing might not occur for all gene products. This keeps open the possibility that X and Y sperm may differ in proteins, but until now, this has not been confirmed by comparative studies between flow-cytometrically sorted X and Y sperm for H-Y antigen or other membrane proteins.