Maternal microchimerism protects against the development of asthma

From Womb to World: Exploring the Immunological Connections between Mother and Child

Mother and child are immunologically interconnected by mechanisms that we are only beginning to understand. During pregnancy, multiple molecular and cellular factors of maternal origin are transferred across the placenta and influence the development and function of the fetal and newborn immune system. Altered maternal immune states arising from pregnancy-associated infections or immunizations have the potential to program offspring immune function in ways that may have long-term health consequences. In this study, we review current literature on the impact of prenatal infection and vaccination on the developing immune system, highlight knowledge gaps, and look to the horizon to envision maternal interventions that could benefit both the mother and her child.

Maternal vaccination: shaping the neonatal response to pertussis

Antepartum maternal vaccination can protect highly sensitive newborns before they are old enough to receive their own vaccines. Two vaccines are currently recommended during pregnancy: the flu vaccine and the Tdap vaccine against tetanus, diphtheria, and pertussis. Although there is strong evidence that maternal vaccination works to protect the offspring, limitations in the understanding of vaccines and of maternal transfer of immunity compound to obscure our understanding of how they work. Here we focus on the example of pertussis to explore the possible mechanisms involved in the transfer of protection to offspring and how these may impact the newborn's response to future exposure to pertussis. For example, Tdap vaccines induce pathogen specific antibodies, and those antibodies are known to be transferred from mother to the fetus in utero and to the newborn via milk. But antibodies alone have modest impact on pertussis disease, and even less effect on colonization/transmission. Maternal immune cells can also be transferred to offspring and may play a direct role in protection from disease and/or influence the developing neonatal immune system. However, some of the transferred immunity may also blunt the offspring's response to subsequent vaccination. In this review we will summarize the protection conferred to offspring by maternal vaccination against pertussis and the likely mechanisms by which protection is transferred, identifying the many knowledge gaps that limit our most effective application of this approach.

Postnatal depletion of maternal cells biases T lymphocytes and natural killer cells' profiles toward early activation in the spleen

The maternal cells transferred into the fetus during gestation persist long after birth in the progeny. These maternal cells have been hypothesized to promote the maturation of the fetal immune system in utero but there are still significant gaps in our knowledge of their potential roles after birth. To provide insights into these maternal cells' postnatal functional roles, we set up a transgenic mouse model to specifically eliminate maternal cells in the neonates by diphtheria toxin injection and confirmed significant depletion in the spleens. We then performed immunophenotyping of the spleens of two-week-old pups by mass cytometry to pinpoint the immune profile differences driven by the depletion of maternal cells in early postnatal life. We observed a heightened expression of markers related to activation and maturation in some natural killer and T cell populations. We hypothesize these results to indicate a potential postnatal regulation of lymphocytic responses by maternal cells. Together, our findings highlight an immunological influence of maternal microchimeric cells postnatally, possibly protecting against adverse hypersensitivity reactions of the neonate at a crucial time of new encounters with self and environmental antigens.

Asthma and the Missing Heritability Problem: Necessity for Multiomics Approaches in Determining Accurate Risk Profiles

Asthma is ranked among the most common chronic conditions and has become a significant public health issue due to the recent and rapid increase in its prevalence. Investigations into the underlying genetic factors predict a heritable component for its incidence, estimated between 35% and 90% of causation. Despite the application of large-scale genome-wide association studies (GWAS) and admixture mapping approaches, the proportion of variants identified accounts for less than 15% of the observed heritability of the disease. The discrepancy between the predicted heritable component of disease and the proportion of heritability mapped to the currently identified susceptibility loci has been termed the ‘missing heritability problem.’ Here, we examine recent studies involving both the analysis of genetically encoded features that contribute to asthma and also the role of non-encoded heritable characteristics, including epigenetic, environmental, and developmental aspects of disease. The importance of vertical maternal microbiome transfer and the influence of maternal immune factors on fetal conditioning in the inheritance of disease are also discussed. In order to highlight the broad array of biological inputs that contribute to the sum of heritable risk factors associated with allergic disease incidence that, together, contribute to the induction of a pro-atopic state. Currently, there is a need to develop in-depth models of asthma risk factors to overcome the limitations encountered in the interpretation of GWAS results in isolation, which have resulted in the missing heritability problem. Hence, multiomics analyses need to be established considering genetic, epigenetic, and functional data to create a true systems biology-based approach for analyzing the regulatory pathways that underlie the inheritance of asthma and to develop accurate risk profiles for disease.

Factors influencing maternal microchimerism throughout infancy and its impact on infant T cell immunity

Determinants of the acquisition and maintenance of maternal microchimerism (MMc) during infancy and the impact of MMc on infant immune responses are unknown. We examined factors which influence MMc detection and level across infancy and the effect of MMc on T cell responses to BCG vaccination in a cohort of HIV exposed, uninfected and HIV unexposed infants in South Africa. MMc was measured in whole blood from 58 infants using a panel of quantitative PCR assays at day one and 7, 15, and 36 weeks of life. Infants received BCG at birth, and selected whole blood samples from infancy were stimulated in vitro with BCG and assessed for polyfunctional CD4+ T cell responses. MMc was present in most infants across infancy with levels ranging from 0-1,193/100,000 genomic equivalents and was positively impacted by absence of maternal HIV, maternal-infant HLA compatibility, infant female sex, and exclusive breastfeeding. Initiation of maternal antiretroviral therapy prior to pregnancy partially restored MMc levels in HIV exposed, uninfected infants. Birth MMc was associated with an improved polyfunctional CD4+ T cell response to BCG. These data emphasize that both maternal and infant factors influence MMc, which may subsequently impact infant T cell responses.

High Frequency of Post-Transfusion Microchimerism Among Multi-Transfused Beta-Thalassemic Patients

Background

Transfusion-associated microchimerism implies the presence of allogeneic hematopoietic cells in an individual, following the transfusion of a blood product. It is a transfusion-related adverse effect/long-term consequence, which has not been well-investigated among regularly transfused patients with thalassemia.

Patients and Methods

We investigated 64 regularly transfused, homozygous β-thalassemic patients and 21 never-transfused healthy volunteer blood donors (controls) for the presence of microchimerism in their sera, using real-time PCR targeting circulating allogeneic, both, Human Leukocyte Antigen-DR isotype (HLA-DR) and non-HLA alleles. The investigation was longitudinally repeated in patient subsets for more than 2 years. Results were correlated with clinical and laboratory parameters, peripheral blood lymphocyte immunophenotype, blood storage time, and donor's gender to identify potential contributing factors for microchimerism generation.

Results

Overall, microchimerism was detected in 52 of the 64 patients (81.2%) and in 6 of the 21 controls (28.5%, p = 0.0001). Forty-four patients (68.7%) exhibited long-term microchimerism (persisted for more than 6 months), confirmed at all time-points investigated. Microchimerism was more frequent among elderly, women, splenectomized and more heavily transfused patients, and among those who exhibit higher serum ferritin levels. In these patients, a distinct descending pattern of CD16^dim+CD56^dim+ natural killer (NK)-cells (p < 0.001) and an ascending pattern of CD4+CD25^brightCD127– regulatory T-cells (p = 0.022) for increasing allelic burden were noticed, suggesting the establishment of recipient immune tolerance against the donor-derived chimeric alleles. Both splenectomized and non-splenectomized thalassemic patients exhibited the same trend. The storage time of transfused blood products and donor/gender mismatch had no impact on the development of microchimerism.

Discussion-Conclusive Remarks

Transfusion-associated microchimerism appears to be a very common complication among multi-transfused thalassemic patients. The potential clinical consequences of this phenomenon remain as yet unclear. Immune tolerance attributed to disease itself and to repeated transfusions might at least in part explain its appearance.

Inherent maternal type 2 immunity: Consequences for maternal and offspring health

An inherent elevation in type 2 immunity is a feature of maternal and offspring immune systems. This has diverse implications for maternal and offspring biology including influencing success of pregnancy, offspring immune development and maternal and offspring ability to control infection and diseases such as allergies. In this review we provide a broad insight into how this immunological feature of pregnancy and early life impacts both maternal and offspring biology. We also suggest how understanding of this axis of immune influence is and may be utilised to improve maternal and offspring health.

Predictors of maternal-origin microchimerism in young women in the Philippines

OBJECTIVES

Microchimerism is the presence of a small quantity of cells or DNA from a genetically distinct individual. This phenomenon occurs with bidirectional maternal-fetal exchange during pregnancy. Microchimerism can persist for decades after delivery and have long-term health implications. However, little is known about why microchimerism is detectable at varying levels in different individuals. We examine the variability and the following potential determinants of maternal-origin microchimerism (MMc) in young women in the Philippines: gestational duration (in utero exposure to MMc), history of being breastfed (postpartum exposure to MMc), maternal telomere length (maternal cells' ability to replicate and persist), and participant's pregnancies in young adulthood (effect of adding fetal-origin microchimerism to preexisting MMc).

MATERIALS AND METHODS

Data are from the Cebu Longitudinal Health and Nutrition Survey, a population-based study of infant feeding practices and long-term health outcomes. We quantified MMc using quantitative PCR (qPCR) in 89 female participants, ages 20-22, and analyzed these data using negative binomial regression.

RESULTS

In a multivariate model including all predictors, being breastfed substantially predicted decreased MMc (detection rate ratio = 0.15, p = 0.007), and there was a trend of decreasing MMc in participants who had experienced more pregnancies (detection rate ratio = 0.55, p = 0.057).

DISCUSSION

These results might be explained by breastfeeding having lasting impact on immune regulatory networks, thus reducing MMc persistence. MMc may also decrease in response to the introduction of fetal-origin microchimerism with pregnancies experienced in adulthood.

Donor white blood cell survival and cytokine profiles following red blood cell transfusion in Australian major trauma patients

BACKGROUND

The potential for the co-existence of genetically disparate cells (microchimerism) and associated cytokine profiles following red blood cell (RBC) transfusion in trauma patients has not been well characterized to date. This study investigated the incidence of surviving donor white blood cells (known as transfused-associated microchimerism (TAM)) and cytokine changes following blood transfusion in trauma patients.

STUDY DESIGN AND METHODS

Trauma patients with an injury severity score (ISS) >12 who had been transfused between 2012-2016 with at least 5 units of RBC units over a 4 h period were recruited. Trauma patients with ISS > 12 who did not require blood transfusion were recruited as controls. The incidence of TAM was determined using a panel of insertion/deletion (InDel) bi-allelic polymorphisms. Selected pro- and anti-inflammatory cytokine profiles were analyzed using cytometric bead array.

RESULTS

The transfused cohort (n = 40) had median ISS of 28 [12-66], received a median of 11 RBC units [4-114] and had median hospital length of stay of 35 days [1-152]. Only 11 (27.5%) patients returned for follow-up blood sampling after discharge. Of these, one patient showed an InDel pattern indicating the presence of TAM. No patients in the control cohort (n = 49) showed TAM. Cytokines IL-10 and IL-6 were found to be elevated in the transfused trauma patients.

CONCLUSION

In this cohort, TAM was found to occur in one patient of the 11 who received a blood transfusion. Elevated IL-6 and IL-10 cytokines were detected in those patients who were transfused. However, the incidence of TAM could not be correlated with the elevated cytokine profiles for this cohort.

Role of PCDH 1 Gene in the Development of Childhood Asthma and Other Related Phenotypes: A Literature Review

The asthma gene PCDH 1, encoding protocadherin-1, is a cellular adhesion molecule which plays an important role in epithelial barrier formation and repair. PCDH 1 is a novel susceptible gene not only in childhood asthma but also in eczema and other atopic phenotypes. In this article, we reviewed relevant articles from PubMed, Google Scholar, Science Direct and included all available significant pieces of information about the PCDH 1 association with asthma and other atopic or non-atopic phenotypes. It is very interesting that cigarette smoking can induce changes in PCDH 1 expression but how the changes in PCDH 1 induce asthma is still not clear. PCDH 1 gene polymorphism also sometimes plays role in asthma and bronchial hyperresponsiveness (BHR) pathogenesis as well as in allergic dermatitis.

Prenatal Allogeneic Tolerance in Mice Remains Stable Despite Potent Viral Immune Activation

Transplanting stem cells before birth offers an unparalleled opportunity to initiate corrective treatment for numerous childhood diseases with minimal or no host conditioning. Although long-term engraftment has been demonstrated following in utero hematopoietic cellular transplantation during immune quiescence, it is unclear if prenatal tolerance becomes unstable with immune activation such as during a viral syndrome. Using a murine model of in utero hematopoietic cellular transplantation, the impact of an infection with lymphocytic choriomeningitis virus on prenatal allospecific tolerance was examined. The findings in this report illustrate that established mechanisms of donor-specific tolerance are strained during potent immune activation. Specifically, a transient reversal in the anergy of alloreactive lymphocytes is seen in parallel with the global immune response toward the virus. However, these changes return to baseline following resolution of the infection. Importantly, prenatal engraftment remains stable during and after immune activation. Collectively, these findings illustrate the robust nature of allospecific tolerance in prenatal mixed chimerism compared with models of postnatal chimerism and provides additional support for the prenatal approach to the treatment of congenital benign cellular disease.

Leukodepleted blood components do not remove the potential for long-term transfusion-associated microchimerism in Australian major trauma patients

Despite the introduction of leukodepleted blood components, it has been shown that donor leukocyte engraftment (microchimerism) remains a long-term consequence of red blood cell (RBC) transfusion. The incidence of microchimerism may be affected by international disparities in blood processing methods or variations in transfusion practices. This study was conducted to determine the prevalence of microchimerism in Australian trauma patients. A secondary aim was to examine whether any patient complications correlated to the incidence of microchimerism. Australian trauma patients (n = 86) who had been transfused with red blood cell (RBC) units between 2000 and 2012 with an injury severity score (ISS) of greater than 15 were recruited. The prevalence of microchimerism was determined using genetic screening with a panel of insertion/deletion biallelic polymorphisms. The mean storage age of the transfused RBC units was 20 ± 8 days and the mean length of stay (LOS) in hospital was 40 ± 39 days. There were no significant associations in this study sample to bias for patient age, gender, number of transfused RBC units or ISS. Nine of the 55 (16.3%) patients transfused with non-leukodepleted blood components displayed an incidence of microchimerism. Of the 31 patients transfused with leukodepleted RBC units, 3 (9.6%) displayed an incidence of microchimerism. Therefore, despite the universal introduction of leukodepleted blood components in Australia, the prevalence of transfusion-associated microchimerism was found to be unchanged. Furthermore, half of the patients exhibiting microchimerism were recorded to have had splenic injury or required splenectomy at the time of transfusion.

Asthma and the otolaryngologist

BACKGROUND

Asthma is a chronic inflammatory disease of the lower airway that is commonly encountered by the otolaryngologist. This article provides information on how to recognize patients with asthma and discuss issues related to diagnosis, treatment, and continued management within the context of current guidelines.

METHODS

A literature review was conducted and relevant sources are referenced concerning the epidemiology of asthma, the pathophysiology of asthma, diagnostic strategies, treatment options, and continued management.

RESULTS

Asthma is a common condition worldwide and is often associated with other atopic diseases such as allergic rhinitis and eczema, though other genetic and environmental factors appear to be important as well. The lower airway and upper airways share similar histology, as well as patterns of inflammation in response to environmental triggers. The diagnosis of asthma involves a careful history and a complete physical exam, including auscultation of the lungs and pulmonary function testing. Pharmacotherapy represents the primary method of treating asthma, though current evidence supports a positive role for antigen-specific immunotherapy for both prevention and treatment. Guidelines are available that can assist the otolaryngologist in classifying the severity of asthma, determining the level of control and recommending modifications in the treatment plan.

CONCLUSION

As airway specialists, otolaryngologists are in a unique position to recognize and manage asthma in their patients, particularly those with allergic disease. Maintaining a high index of suspicion and understanding the key elements of diagnosis and treatment are extremely important in order to achieve this goal.

Advancing the detection of maternal haematopoietic microchimeric cells in fetal immune organs in mice by flow cytometry

Maternal microchimerism, which occurs naturally during gestation in hemochorial placental mammals upon transplacental migration of maternal cells into the fetus, is suggested to significantly influence the fetal immune system. In our previous publication, we explored the sensitivity of quantitative polymerase chain reaction and flow cytometry to detect cellular microchimerism. With that purpose, we created mixed cells suspensions in vitro containing reciprocal frequencies of wild type cells and cells positive for enhanced green fluorescent protein or CD45.1⁺, respectively. Here, we now introduce the H-2 complex, which defines the major histocompatibility complex in mice and is homologous to HLA in human, as an additional target to detect maternal microchimerism among fetal haploidentical cells. We envision that this advanced approach to detect maternal microchimeric cells by flow cytometry facilitates the pursuit of phenotypic, gene expression and functional analysis of microchimeric cells in future studies.

Childhood asthma: recent developments and update

PURPOSE OF REVIEW

The purpose of this review is to provide an update on childhood asthma specifically related to the underlying genetic background and pathophysiology of asthma and their interaction with environmental stimuli. We will also discuss emerging data in the field of disease phenotyping.

RECENT FINDINGS

The field of genetics is continuously evolving to expand our knowledge on the cause of disease. Childhood onset asthma has been related to atopy and exposure to early-life infections. More recently, phenotypes have been used to classify asthma as transient and persistent, but the association of each phenotype with the genetic origin of asthma is not clearly understood.

SUMMARY

This review covers the topics of genetics, epigenetics, pathophysiology, phenotypes and treatment as they relate to childhood asthma. Overall, it provides a basis for the future of asthma treatment through description of the current research.

Advances in pediatric asthma in 2013: coordinating asthma care

Last year's "Advances in pediatric asthma: moving toward asthma prevention" concluded that "We are well on our way to creating a pathway around wellness in asthma care and also to utilize new tools to predict the risk for asthma and take steps to not only prevent asthma exacerbations but also to prevent the early manifestations of the disease and thus prevent its evolution to severe asthma." This year's summary will focus on recent advances in pediatric asthma on prenatal and postnatal factors altering the natural history of asthma, assessment of asthma control, and new insights regarding potential therapeutic targets for altering the course of asthma in children, as indicated in Journal of Allergy and Clinical Immunology publications in 2013 and early 2014. Recent reports continue to shed light on methods to understand factors that influence the course of asthma, methods to assess and communicate levels of control, and new targets for intervention, as well as new immunomodulators. It will now be important to carefully assess risk factors for the development of asthma, as well as the risk for asthma exacerbations, and to improve the way we communicate this information in the health care system. This will allow parents, primary care physicians, specialists, and provider systems to more effectively intervene in altering the course of asthma and to further reduce asthma morbidity and mortality.

Advances in adult asthma diagnosis and treatment in 2013

In 2013, several themes emerged: (1) a dedicated search for new therapies using new mechanisms; (2) the importance of the plasticity of the immune system (eg, that molecules that mediate inflammation in one setting can promote its resolution and return to homeostasis in other circumstances); (3) the complex role of viruses in asthma exacerbations; (4) the similarities and differences among asthma, asthma in smokers, and chronic obstructive pulmonary disease; and (5) the importance of understanding asthma phenotypes and their stability over time. Once new therapeutics pass the initial clinical trials, patient-oriented and real-world research will be needed.