p107 is a suppressor of retinoblastoma development in pRb-deficient mice

Hemizygosity for the retinoblastoma gene RB in man strongly predisposes to retinoblastoma. In the mouse, however, Rb hemizygosity leaves the retina normal, whereas in Rb^−/− chimeras pRb-deficient retinoblasts undergo apoptosis. To test whether concomitant inactivation of the Rb-related gene p107 is required to unleash the oncogenic potential of pRb deficiency in the mouse retina, we inactivated both Rb and p107 by homologous recombination in embryonic stem cells and generated chimeric mice. Retinoblastomas were found in five out of seven adult pRb/p107-deficient chimeras. The retinal tumors showed amacrine cell differentiation, and therefore originated from cells committed to the inner but not the outer nuclear layer. Retinal lesions were already observed at embryonic day 17.5. At this stage, the primitive nuclear layer exhibited severe dysplasia, including rosette-like arrangements, and apoptosis. These findings provide formal proof for the role of loss of Rb in retinoblastoma development in the mouse and the first in vivo evidence that p107 can exert a tumor suppressor function.     

Epithelioid trophoblastic tumor: clinicopathological features with an emphasis on uterine cervical involvement.

We report on the clinical and histological features of five cases of epithelioid trophoblastic tumor, with an emphasis on its involvement of the uterine cervix. All five patients were of reproductive age (median age 38.4 years) and all, except one, presented with vaginal bleeding 3 to 18 years after the most recent pregnancy. One patient presented with amenorrhea. Elevation of serum human chorionic gonadotropin (hCG) was seen in four cases. Pathologically, the tumor involved endocervix in three cases and involved uterine corpus in another two. All five tumors were invasive, nodular lesions consisting of epithelioid intermediate trophoblastic cells that were mononuclear with abundant eosinophilic cytoplasm, along with zones of hyaline material and necrotic debris. In three cases of cervical involvement, the neoplastic cells focally replaced endocervical surface and glandular epithelium, simulating high-grade squamous intraepithelial lesions. Immunohistochemically, all five tumors displayed focal positivity for human placental lactogen and hCG. Positive nuclear staining of p63 was seen in all five cases. All patients received total hysterectomy and various regimes of adjuvant chemotherapy. Three patients survived the tumor with no recurrences or metastases with follow-up periods of 3, 7 and 16 years. One patient is currently alive with lung metastasis 1 month after the surgery. One patient died of tumor metastasis 8 months after the diagnosis. In summary, with its unusual ability to simulate an invasive squamous cell carcinoma and other epithelioid neoplasms, epithelioid trophoblastic tumor frequently poses a diagnostic challenge, especially when involving the uterine cervix. High index of suspicion and an awareness of elevation of serum chorionic gonadotropin are crucial in reaching a correct diagnosis.     

Use of the Hasson cannula producing major vascular injury at laparoscopy

Despite the recent demonstration that vascular lesions occur significantly more frequently in patients having closed rather than "open" laparoscopy, there never has been a published case report of injury to the great vessels associated with the open technique of initial access to the peritoneal cavity at laparoscopy. We present the first two such cases reported, along with a brief review of the literature related to such major vascular injuries (MVI) sustained at laparoscopy. Lacking appreciation of aortic anatomy and intraoperative technical factors contribute to the occurrence of these injuries. Delayed diagnosis and management contribute to poor outcomes. Secondary injury frequently is associated with MVI at laparoscopy.     

Immunomodulation of transplant rejection using monoclonal antibodies and soluble receptors

The main objective of our studies has been to optimize the effects of monoclonal antibodies (MAbs) and other immunosuppressive reagents to enhance organ graft survival. One such agent is OKT3, a MAb that is directed against the CD3 component of the human T-cell receptor (TCR) complex. Treatment of a rejection episode with OKT3 results in a rapid and efficient clearing of circulating T cells and reversal of most rejection episodes. Its wider use in transplantation and in the treatment of immune-mediated disease is limited by adverse reactions that follow the initial dose, the production of neutralizing Abs, and the transient nature of the immunosuppression. We have engineered CDR-grafted humanized anti-CD3 MAbs that lack Fc-receptor binding activity through mutagenesis of amino acids in the Fc portion of the MAb. This results in an immunosuppressive anti-CD3 MAb that is less antigenic and one that does not induce the first-dose side effects. In addition, we have pursued a goal of developing a therapy that will induce donor-specific tolerance while maintaining overall recipient immune competency. Because antigen-specific T-cell activation depends not only on TCR-ligand interaction, but also on additional costimulatory signals mediated by accessory molecules such as CD28, blocking the binding of CD28 on T cells to its ligand B7, during TCR engagement, might modulate transplantation responses. Using a soluble fusion protein of human CTLA4, CTLA4-Ig, that binds B7 with high affinity, inhibition of human pancreatic islet rejection that occurs, at least in part, by affecting T-cell recognition of human B7⁺ antigen-presenting cells has been demonstrated. In addition, CTLA4-Ig induces long-term, donor-specific unresponsiveness.     

Protective Immunity against Recurrent Staphylococcus aureus Skin Infection Requires Antibody and Interleukin-17A

Although many microbial infections elicit an adaptive immune response that can protect against reinfection, it is generally thought that Staphylococcus aureus infections fail to generate protective immunity despite detectable T and B cell responses. No vaccine is yet proven to prevent S. aureus infections in humans, and efforts to develop one have been hampered by a lack of animal models in which protective immunity occurs. Our results describe a novel mouse model of protective immunity against recurrent infection, in which S. aureus skin and soft tissue infection (SSTI) strongly protected against secondary SSTI in BALB/c mice but much less so in C57BL/6 mice. This protection was dependent on antibody, because adoptive transfer of immune BALB/c serum or purified antibody into either BALB/c or C57BL/6 mice resulted in smaller skin lesions. We also identified an antibody-independent mechanism, because B cell-deficient mice were partially protected against secondary S. aureus SSTI and adoptive transfer of T cells from immune BALB/c mice resulted in smaller lesions upon primary infection. Furthermore, neutralization of interleukin-17A (IL-17A) abolished T cell-mediated protection in BALB/c mice, whereas neutralization of gamma interferon (IFN-γ) enhanced protection in C57BL/6 mice. Therefore, protective immunity against recurrent S. aureus SSTI was advanced by antibody and the Th17/IL-17A pathway and prevented by the Th1/IFN-γ pathway, suggesting that targeting both cell-mediated and humoral immunity might optimally protect against secondary S. aureus SSTI. These findings also highlight the importance of the mouse genetic background in the development of protective immunity against S. aureus SSTI.     

Polymorphisms in BACE2 may affect the age of onset Alzheimer's dementia in Down syndrome

It is known that Alzheimer's disease (AD) presents at an early age in people with Down syndrome (DS). The trisomy 21 in DS provides an opportunity to study the effect of duplicated genes in AD. APP and BACE2 are 2 genes located in chromosome 21 and related to AD. We looked into our cohort of 67 DS cases with dementia for the effect of BACE2 variants in age of onset of dementia. Of the 83 single-nucleotide polymorphisms (SNPs), 6 were associated with age of onset and another 8 SNPs were borderline associated. Our finding also replicated a previous study showing association of rs2252576 with AD.     

B-cell maturation antigen-specific chimeric antigen receptor T cells for multiple myeloma: Clinical experience and future perspectives

Despite major advances in the treatment of multiple myeloma (MM), it remains a largely incurable disease with long-term control often dependent on continuous therapy. More effective, better tolerated treatments are therefore required to achieve durable remissions and to improve the quality of life of MM patients. Adoptive immunotherapy employing T cells expressing chimeric antigen receptors (CAR) is currently among the most promising treatment approaches in cancer. Within the target portfolio for MM immunotherapy, B-cell maturation antigen (BCMA) is among the most widely studied target antigens. BCMA is consistently expressed on MM cells and, importantly, is not expressed in critical healthy tissue. For this reason, it is an ideal target for MM immunotherapy. Several clinical trials evaluating different BCMA-targeting CAR constructs have been initiated and early results are very promising. However, in this rapidly developing clinical landscape, the ultimate role of BCMA-specific CAR-T cell therapy remains unclear. In this review, we will summarize currently available clinical data on BCMA-directed CAR-T cells and discuss potential future perspective for this promising treatment approach in MM.     

Maternal–Fetal Interactions Focus: Toward an understanding of allogeneic conflict in pregnancy and transplantation

Pregnancy is recognized as a spontaneously acquired state of immunological tolerance by the mother to her semi-allogeneic fetus, but it is a major cause of allosensitization in candidates for organ transplantation. This sensitization, assessed by the presence of anti-HLA IgG, contributes to sex disparity in access to transplantation and increases the risk for rejection and graft loss. Understanding this dual tolerance/sensitization conundrum may lead to new strategies for equalizing access to transplantation among sexes and improving transplant outcomes in parous women. Here, we review the clinical evidence that pregnancy results in humoral sensitization and query whether T cell responses are sensitized. Furthermore, we summarize preclinical evidence on the effects of pregnancy on fetus-specific CD4⁺ conventional, regulatory, and CD8⁺ T cells, and humoral responses. We end with a discussion on the impact of the divergent effects that pregnancy has upon alloantigen re-encounter in the context of solid organ transplantation, and how these insights point to a therapeutic roadmap for controlling pregnancy-dependent allosensitization.

IntroductionThe fact that multiple successive pregnancies with the same male partner can be brought to term successfully suggests that the immunological response to a semi-allogeneic fetus is diametrically opposite to the responses elicited by genetically comparable transplanted organs. Peter Medawar in 1953 (Medawar, 1953) discussed this “immunological paradox of pregnancy,” and since then, there have been extensive investigations into how the fetus avoids rejection. A plethora of immune regulatory mechanisms has been uncovered within the uterine environment, including enrichment in regulatory T cells (Tregs), natural killer cells, regulatory macrophages, entrapment of APCs, and chemokine gene silencing of decidual stromal cells (PrabhuDas et al., 2015). Systemic factors that prevent fetal rejection have also been identified, including immune modulation by pregnancy-related hormones and release of tolerogenic placental debris, which may contribute to the preferential systemic expansion of fetus-specific Tregs and acquired dysfunction by conventional T cells (Tconvs) and CD8⁺ T cells. Since the majority of these mechanisms either act locally or only during pregnancy, it was assumed that T cell tolerance would manifest itself only in the context of subsequent pregnancy, and that encounter with the same alloantigens in the context of a solid organ transplant, in the absence of local or systemic pregnancy-induced immunomodulation, would trigger allograft rejection.The emphasis on T cells as the major mediator of allograft rejection and on T cell tolerance as a means to achieve transplantation tolerance parallels the focus on the constraint of T cells in pregnancy. Thus, despite studies in the 1980s by Bell and Billington (Bell and Billington, 1981; Bell and Billington, 1983; Bell and Billington, 1986) that pregnancy can elicit paternal-reactive antibodies, how pregnancy sensitizes B cell responses while maintaining T cell tolerance to the semi-allogeneic fetus has remained an under-investigated topic in preclinical models (PrabhuDas et al., 2015). In contrast and driven by the ease in quantifying HLA-specific antibodies but difficulty in assessing HLA-specific T cell responses, clinical studies in solid organ transplantation have revealed that pregnancy is a highly sensitizing event that results in the production of fetus-reactive anti-HLA antibodies, and the presence of these antibodies limits access to transplantation and contributes to increased risk of transplant rejection. In this review, we focus on the contrasting effects of pregnancy on these two arms of the adaptive immune system, and on how these pregnancy-shaped responses are recalled by alloantigens that are shared between offspring and transplanted allograft.Clinical impact of pregnancy alloimmunization in organ transplantationHumoral sensitizationThe effect of pregnancy on the immune system was first reported by J.J. Rodd in 1959 when he described peripartum women experiencing an increased number of blood transfusion reactions (Van Rood et al., 1958). It was this observation that allowed for the discovery of anti-HLA antibodies from the sera of pregnant women (Van Rood et al., 1958). Anti-HLA antibodies are produced during the first trimester of a pregnancy and increase in titer over the gestational course and with multiple pregnancies (Lee et al., 2011). During the postpartum phase, antibody levels rise in the first 90 d and gradually disappear in 50% of postpartum women over a 1–2 yr period (Cecka, 2010; Masson et al., 2013). Anti-HLA antibody titers following kidney transplantation increase more robustly in patients having had prior pregnancies than in those having received previous transplantation or transfusion, suggestive of robust pregnancy-induced memory B cells (Higgins et al., 2015). Notably, although pregnancy-induced alloantibodies can diminish with time, alloreactive memory T and B cells can persist (Senn et al., 2021). Thus, anti-HLA antibodies and memory B cells induced by semi-allogeneic pregnancies play a pivotal role prior to and after transplantation, especially for multiparous women.Historically, anti-HLA antibody titers were measured by the panel-reactive antibody (PRA) technique through a complement-dependent cytotoxicity assay; however, the major limitation of this method is its inconsistency and lack of HLA specificity. In 2009, the United Network for Organ Sharing implemented measuring sensitization using single HLA-coated beads, an assay that precisely identifies specific HLA antigen targets (Cecka, 2010). A computer algorithm generates a calculated PRA (cPRA) according to the HLA frequencies derived from the donor population with the goal of providing consistently accurate results on the extent of sensitization of transplant candidates and the chances for a highly sensitized candidate to find a compatible organ donor. Around 30% of pregnant women are sensitized when measured via complement-dependent cytotoxicity assay, whereas 50–75% of women were found to be sensitized by pregnancy when the single HLA bead assay was used (Bromberger et al., 2017). Furthermore, a retrospective analysis of the United Network for Organ Sharing registry’s waitlist pool showed that individuals with a cPRA >98% were over-represented by women by ~60% (Redfield et al., 2016). Cumulatively, these data reveal the detrimental impact of pregnancy in women in need of a transplant and the disparity it creates toward identifying a suitable donor organ and having a successful post-transplantation course.Living donor kidney transplantation has better outcomes compared to kidney transplantation from deceased donors (Roodnat et al., 2003). However, 30% fewer women received living donor kidney transplantation as compared with men despite comparable referrals (Bromberger et al., 2017; Roodnat et al., 2003). Pregnancy was identified as a major contributor to this disparity, as postpartum women were increasingly incompatible with their spouse and offspring compared with men (Bromberger et al., 2017). Furthermore, parous women are at a higher risk of being sensitized to unrelated donors sharing an allele of the partner or offspring (Gibney et al., 2006; Vaidya et al., 2006). Child-specific sensitization measured by single-HLA bead assay was detected at the HLA-A/B/C/DR loci in 28–38% of 301 multiparous women analyzed (Honger et al., 2013), with child-specific HLA-B loci being the most sensitizing followed by HLA-A > HLA-DRB1 > HLA-C (Dankers et al., 2003; Honger et al., 2013). Furthermore, by quantifying mother/child mismatches by the number of mismatched HLA eplets, where an eplet is defined as the cluster of amino acids representing the smallest functional unit of structural epitopes on the HLA molecule targeted by B cell receptor and antibodies, the rate of child-specific sensitization increased with the presence of ≥20 mismatched eplets (Honger et al., 2013). These observations are reminiscent of eplet-load mismatch between the organ donor and the recipient predicting de novo anti-HLA antibody production by the host and reduced graft survival, and thus underscories the detrimental effects of pregnancy-induced humoral sensitization (Philogene et al., 2020; Sapir-Pichhadze et al., 2020).T cell sensitizationIn contrast to the abundant evidence that fetus-specific B cell responses are induced during pregnancy and the barrier they pose to transplantation, the effects of pregnancy-induced effector T cell responses on subsequent transplantation are more opaque. Specifically, although it is clear that maternal T cells acquire tolerance to the semi-allogeneic fetus, it is uncertain whether this T cell tolerance extends to subsequent organ allografts sharing antigens with the fetus. Early observations that fetal-derived stem cells can persist in low numbers in the mother’s circulation for as long as 27 yr, a phenomenon termed peripheral fetal microchimerism (Nelson, 1998), prompted the hypothesis that this microchimerism mediates long-term fetus-specific tolerance in mothers and promotes the acceptance of grafts from their offspring (Starzl et al., 1993). However, several studies testing the correlation between donor/recipient kinship and allograft fate have reported comparable outcomes between groups receiving grafts from offspring versus non-offspring (Cohen et al., 2018; Ghafari, 2008; Mahanty et al., 2001). A recent retrospective analysis performed using the Organ Procurement and Transplant Network living donor liver transplant database revealed that 1-, 5- and 10-yr allografts and patient survival was poorer among mothers who received the organ from their offspring as compared with unrelated living donors (Dagan et al., 2020). A major caveat of such studies is the potential pro-rejection effects of pregnancy-sensitized B cells even when pregnancy-induced antibodies have diminished; as a result, the contribution of pregnancy-primed T cells, either pro-rejection or pro-tolerogenic, may be obscured. Indeed, Senn et al. (2021) reported that women with prior pregnancies receiving kidneys from their husband consistently had a higher rate of antibody-mediated rejection compared with women with prior pregnancies receiving kidneys from other living or deceased donors.A limited number of studies have attempted to directly quantify ex vivo donor-specific T cell responses arising during normal human pregnancy using proliferation, cytokine production, or cellular cytotoxicity as readouts. When IL-4 and IFNγ ELISPOT assays were used to quantify PBMC responses from non-pregnant versus pregnant women to paternal or pooled alloantigens, Mjosberg et al. (2007) reported that pregnancy did not result in increased paternal-specific IL-4 or IFNγ responses. Furthermore, removal of Tregs resulted in non-specific increases in IFNγ responses and paternal-specific augmentation in IL-4 production. Collectively, their study suggested an absence of pregnancy-specific sensitization of T cells, while also hinting at postpartum Tregs controlling fetus-specific IL-4 responses and broadly controlling IFNγ responses. Notably, reduced frequencies of circulating FoxP3⁺ Tregs were observed with spontaneous preterm birth, preeclampsia, and recurrent spontaneous miscarriages compared to healthy pregnancies suggesting a more systemic effect of Tregs (Dimova et al., 2011; Inada et al., 2015; Inada et al., 2013; Kisielewicz et al., 2010; Koucky et al., 2014; Mjosberg et al., 2010; Nadkarni et al., 2016; Schober et al., 2012; Tilburgs et al., 2008; Tsuda et al., 2018).Pregnancy-induced Tregs are critical for promoting both primary and secondary pregnancies by suppressing T cell proliferation and cytokine production not only in secondary lymphoid organs but also in the placenta (Salvany-Celades et al., 2019). Expansion of Tregs in the decidual tissue has been prostulated to suppress fetus-specific responses locally (Tilburgs et al., 2008; Erlebacher, 2013). Notably, three different Treg populations have been identified at the maternal–fetal interface: CD25^HIFOXP3⁺, PD1^HIFOXP3⁻IL-10⁺, and TIGIT⁺FOXP3^dim Tregs. Decidual CD25^HIFOXP3⁺ Tregs were able to suppress the proliferation and IFNγ and TNFα production by CD4⁺ and effector CD8⁺ T cells in vitro, whereas decidual PD1^HI Tregs and TIGIT⁺ Tregs inhibited CD4⁺ but not effector CD8⁺ T cells. However, whether pregnancy-induced Tregs are most potent in the decidua or whether they can also dominantly suppress T cell responses to offspring-matched allografts in secondary lymphoid organs is currently unknown.CD8⁺ T cell responses to fetus-specific minor antigens have been more consistently reported to develop during pregnancy compared to CD4⁺ T cell responses (Linscheid and Petroff, 2013). Lissauer et al. (2012) assayed fetal-specific CD8⁺ cytotoxic responses using MHC-peptide dextramer multimers bearing a HY-immunodominant peptide in women pregnant with a male fetus. These CD8⁺ T cells expanded during pregnancy and persisted in the post-natal period in 50–62% of pregnant women. Furthermore, the fetal-specific CD8⁺ T cells retained their ability to proliferate, secrete IFNγ, and lyse target cells. These observations corroborated previous studies (Bouma et al., 1996; James et al., 2003; Mommaas et al., 2002; Piper et al., 2007; Verdijk et al., 2004) and suggested that fetal-specific CD8⁺ T cells expand during pregnancy and persist postpartum. It is tempting to speculate that preservation of fetus-CD8⁺ T cell responses during pregnancy, especially in the decidua, may have been evolutionarily selected to ensure the development of protective immunity for the developing fetus against viral infections, given that the fetus is haplo-identical to the mother, and thus maternal HLA-restricted CD8⁺ responses will recognize virally infected fetal cells (Tilburgs and Strominger, 2013; van Egmond et al., 2016). Indeed, observations that the decidua contains a higher percentage of CD8⁺ T cells and a lower percentage of CD4⁺ T cells compared with the peripheral blood is consistent with this possibility (Tilburgs et al., 2009; van Egmond et al., 2016).Potentially divergent fates of fetus-specific T cell subsets, together with a paucity of studies examining fetus-specific T cell responses in the extended postpartum period, make it difficult to definitively conclude if pregnancy-primed T cells are functionally tolerant or sensitized to fetal antigens presented in the context of a solid organ transplant. The ex vivo quantification of fetus-specific T cell responses is technically challenging and complicated by the increased frequency of pregnancy-induced Tregs (Salvany-Celades et al., 2019). Furthermore, ex vivo observations may not necessarily predict how these cells will behave in vivo after transplantation with organs sharing HLA antigens with the fetus. In vivo studies in postpartum recipients suggest that poorer outcomes are complicated by pregnancy-induced humoral sensitization (