Microchimerism and human autoimmune diseases

Cells traffic in both directions between the fetus and the mother during pregnancy. Recent studies indicate that a low level of fetal cells commonly persists in the maternal circulation for years after pregnancy completion. The harboring of DNA or cells from another individual at low levels is called microchimerism. Chronic graft-vs-host disease is a condition of human chimerism that shares similarities to some autoimmune diseases and for which the specific HLA genes of donor and host are known to be of central importance. Considered together with the female predilection to autoimmunity, these observations led to the hypothesis that microchimerism and HLA genes of host and non-host cells are involved in autoimmune disease. The hypothesis also extends to men and females who have not been pregnant because there are other sources of microchimerism. Maternal cells are now know to persist in her progeny and microchimerism can also derive from a twin or from a blood transfusion. Studies of systemic sclerosis, primary biliary cirrhosis, Sjögrens syndrome, polymorpyhic eruption of pregnancy, myositis and thyroid disease have both lent support and raised doubts about the role of microchimerism in autoimmune disease.

Polymyositis as a manifestation of chronic graft-versus-host disease

OBJECTIVE

Chronic graft-versus-host disease (GVHD) after haematopoietic stem cell transplantation (HSCT) has similarities to some idiopathic autoimmune diseases, including polymyositis. To investigate the relationship between chronic GVHD and idiopathic myositis we conducted a detailed analysis of all cases of myositis occurring in a large series of HSCT patients.

METHODS

We conducted a retrospective chart review of all cases of myositis that developed in 7161 patients who underwent HSCT at the Fred Hutchinson Cancer Research Center between 1969 and 1999.

RESULTS

Among 1859 individuals who developed chronic GVHD, 12 developed myositis. No patients developed myositis without chronic GVHD. Myositis was first identified between 7 and 55 months after transplantation. In histopathology, electromyography, laboratory values and response to immunosuppressive therapy, the cases resembled idiopathic polymyositis. Autoantibodies were found in eight cases.

CONCLUSIONS

Myositis in the chronic GVHD population occurred with an incidence higher than expected by chance, suggesting that muscle may be a target tissue for chronic GVHD. Recent studies have implicated allogeneic cells persisting after maternal-fetal cell transfer in selected autoimmune diseases, including myositis. This report lends support to the possibility that both idiopathic myositis and chronic GVHD-related myositis could involve allo-autoimmune responses.

HLA relationships of pregnancy, microchimerism and autoimmune disease

Recent studies have established that there is bi-directional cell traffic between mother and fetus during pregnancy. Suprisingly, fetal cells have been found to persist in the maternal circulation for years after pregnancy. Maternal cells can also persist into adult life in her progeny. When cells from one individual are present in the body of another the term chimerism is used and a low level of non-host cells is referred to as microchimerism. Chronic graft-versus-host disease often occurs after stem cell transplantation, is a known condition of chimerism, and resembles spontaneously occurring autoimmune diseases including systemic sclerosis, Sjögren's syndrome, primary biliary cirrhosis and sometimes myositis and systemic lupus. Of central importance to the development of chronic graft-versus-host disease is the HLA relationship of host and donor cells. Considering this constellation of observations together led to the hypothesis that microchimerism and HLA-relationships are involved in the pathogenesis of some autoimmune diseases. Although much additional work is needed, results of initial studies provide support to the concept that non-host cells could participate in the pathogenesis of some autoimmune diseases.

From the simple detection of microchimerism in patients with autoimmune diseases to its implication in pathogenesis

Long-term persistence of fetal cells in parous women (fetal microchimerism, FM) as well as maternal cells in their offspring (maternal microchimerism, MM) have been reported. Systemic sclerosis (SSc), primary biliary cirrhosis (PBC), and Sjögren's syndrome (SS) share similar epidemiology with a predilection for females following childbearing years, with clinical similarities to chronic graft-versus-host disease, a known condition of chimerism. This led to the hypothesis that FM could be involved in the pathogenesis of autoimmune diseases. Initial investigations were conducted in SSc, where the hypothesis was supported by the more frequent occurrence and, quantitatively, a greater degree of FM in women with SSc compared to matched healthy women. Long-term persistence, however, of fetal cells in healthy women indicates that FM per se is not sufficient for causing SSc, but may be important in the context of other risk factors, such as genetic susceptibility and HLA relationship among host and nonhost cells. Contradictory results have recently been published for both PBC and SS and cause difficulty in drawing any conclusions about the role of FM in their pathogenesis. On the other hand, MM has been investigated as a risk factor in patients with systemic lupus (SLE) and juvenile dermatomyositis (JDM). A potential role of MM has been suggested in the pathogenesis of SLE. Recent publications also support the hypothesis that MM might lead to increased risks for JDM. In conclusion, contradictory results have been observed. This reflects a need for standardization of protocols and the selection of control populations. Detection of microchimerism has to be quantitatively studied in the context of genetic factors in order to study its relationship to the pathogenesis of autoimmune diseases.

Fetal cell microchimerism in tissue from multiple sites in women with systemic sclerosis

OBJECTIVE

The realization that fetal cells pass into the maternal circulation and can survive for many years has raised the question of whether fetal microchimerism can cause subsequent disease in the mother. Available data suggest that fetal-maternal transfusion may be related to some autoimmune diseases, notably systemic sclerosis (SSc). The goal of the current work was to identify and quantify tissue-specific fetal microchimerism in women with SSc.

METHODS

We analyzed multiple tissue specimens obtained at autopsy from women with SSc as well as women who had died of causes unrelated to autoimmunity, using fluorescence in situ hybridization to detect the presence of male cells in women with sons. Tissues analyzed included adrenal gland, heart, intestine, kidney, liver, lung, lymph node, pancreas, parathyroid, skin, and spleen.

RESULTS

Male cells were observed in tissue from at least 1 site in each woman with SSc and were found most frequently in spleen sections. After spleen, male cells were observed most frequently in lymph node, lung, adrenal gland, and skin tissue. The only tissue type in which male cells were not seen in any patient was pancreatic tissue. Male cells were not observed in tissue from women who had died of causes unrelated to autoimmunity.

CONCLUSION

The results of this study suggest that fetal cells migrate from the peripheral circulation into multiple organs in women with SSc. All of the women studied had previously given birth to sons, so it is likely that these cells are of fetal origin. While the relevance of this finding to the pathogenesis of SSc remains to be elucidated, the presence of fetal cells in internal organs suggests that they could play a role in disease pathogenesis and that they may preferentially sequester in the spleen. The presence of these male cells may also be a result of disease, possibly through the migration of terminally differentiated and/or progenitor cells to areas of tissue damage.

Microchimerism and hla relationships of pregnancy: Implications for autoimmune diseases

The application of molecular techniques to the study of human pregnancy has resulted in knowledge that the placenta is only a relative barrier to traffic of fetal and maternal cells. Moreover, long-term persistence of fetal cells in the maternal circulation and maternal cells in her progeny have been described. Harboring of cells from another individual is referred to as chimerism and microchimerism indicates low levels of non-host cells. The clinical features of a known condition of human chimerism, chronic graft-versus-host disease that occurs after stem cell transplantation, resemble spontaneously occurring autoimmune diseases including systemic sclerosis, Sjögren's syndrome, primary biliary cirrhosis, and sometimes myositis and systemic lupus. A critical determinant of chronic graft-versus-host disease is the HLA relationship of donor and host cells. When considered together, these observations have led to a new area of research investigating whether microchimerism and HLA-relationships are involved in the pathogenesis of some autoimmune diseases.

Knowledge, authority and identity: a prolegomenon to an epistemology of the clinic

Disputes about theory in bioethics almost invariably revolve around different understandings of morality or practical reasoning; I here suggest that the field would do well to become more explicitly contentious about knowledge, and start the task of putting together a clinical epistemology. By way of providing some motivation for such a discussion, I consider two cases of resistance to shifts in clinical practice that are, by and large, not ethically controversial, highlighting how different conceptions of epistemic authority may contribute to clinicians' unwillingness to adopt these changes, and sketching out some initial suggestions for epistemic analysis of clinical practice.

Forming professional bioethicists: the program at the University of Tennessee, Knoxville

As a way of contributing to bioethics' understanding of itself, and, more particularly, to invigorate conversation about how we can best educate future colleagues, we present here a sketch of the quarter-century-old graduate concentration in medical ethics housed in the Department of Philosophy at the University of Tennessee, Knoxville. Our hope is to incite other programs to share their histories, strategies, problems, and aspirations, so as to help the field as a whole get a clearer sense of how we are putting together our future, and of how we might best go about this important job.

HLA-DQA1*0501 is associated with diffuse systemic sclerosis in Caucasian men

OBJECTIVE

Systemic sclerosis (SSc) is uncommon in men, and relatively little is known about factors contributing to its pathogenesis in this population. In the current study, we investigated HLA class II alleles in men with SSc. We also investigated the hypothesis that HLA compatibility of the mother could be a risk factor for SSc in men.

METHODS

Sequence-specific oligonucleotide probe typing was used to determine DQA1, DQB1, and DRB1 alleles of SSc patients (50 men and 36 parous women), healthy controls (59 men and 80 parous women), 26 mothers of men with SSc, and 44 mothers of healthy men. All study subjects were Caucasian, and allele frequencies were compared with those of Caucasian controls from the Eleventh International Histocompatibility Workshop as well as those of local controls.

RESULTS

The DQA1*0501 allele was significantly increased among men with SSc compared with healthy men (odds ratio [OR] 2.3, P = 0.006, Pcorr = 0.04). DQA1*0501 was associated with diffuse SSc in men (OR 3.0, P = 0.004, Pcorr = 0.03), but not with limited SSc in men. Maternal HLA compatibility was not a risk factor for SSc in men.

CONCLUSION

Previous studies have shown associations of DRB1 alleles with SSc, but have rarely determined DQA1 allele frequencies. Our findings indicate that a specific DQA1 allele is associated with SSc, and that DRB1 associations may be due to linkage disequilibrium with DQA1. Moreover, by analyzing genetic susceptibility according to sex, we found that the contribution of HLA genes to the risk of SSc was substantially greater in men than in parous women.

The effect of task on determination of maximum phonational frequency range

The purpose of this study was to investigate if there was an effect of task on determination of maximum phonational frequency range (MPFR). Two tasks commonly used to elicit MPFR in clinical voice evaluations were compared. Normal adult females (N = 30) were examined. No statistically significant effect of task was found. Both tasks (glissando and discrete-step) were found to have a high positive correlation (0.84). Implications of the use of one task for determination of maximum phonational frequency range are discussed, as is the possibility of a task effect on determination of other voice parameters.

Reproductive ethics and the family

The phrase 'reproductive ethics', as used by bioethicists, typically refers to concerns over morally appropriate employment of assisted reproductive technologies and, perhaps somewhat less commonly, to issues arising from technologies that block conception or end pregnancies. I here recommend to the attention of the field a more commodious use of 'reproductive ethics', one that takes seriously how humans are brought into the world as moral and social beings, and not simply as biological individuals. As a focus for this expanded agenda, I examine prevalent disagreements over the patterns and sources of the responsibilities and prerogatives that help define family structures, both as these are reflected in assisted reproductive practices involving the purchase of gametes, and in U.S. legal controversies about whether parents, or family courts, should determine who has the right to a relationship with children.

Cutting edge: persistent fetal microchimerism in T lymphocytes is associated with HLA-DQA1*0501: implications in autoimmunity

The host's MHC genotype plays a critical role in susceptibility to autoimmune diseases. We previously proposed that persistent fetal microchimerism from pregnancy contributes to the pathogenesis of autoimmune diseases such as scleroderma. In the current study, we investigated whether the specific host MHC genotype is associated with persistent microchimerism among T lymphocytes in women with scleroderma and in healthy women. Fetal microchimerism among T lymphocytes was strongly associated with HLA DQA1*0501 of the mother (odds ratio (OR) = 13.5, p = 0.007, p corrected (pc) = 0.06) and even more strongly with DQA1*0501 of the son (OR = infinity; p = 0. 00002, pc = 0.0002). This is the first description of an association between persistent fetal microchimerism in maternal T lymphocytes and specific HLA class II alleles. Although the association was observed in both healthy women and in women with scleroderma, the finding suggests an additional route by which HLA genes might contribute to susceptibility to autoimmune disease.

Pulsed ultrasound enhances the killing of Escherichia coli biofilms by aminoglycoside antibiotics in vivo

Escherichia coli biofilms on two polyethylene disks were implanted subcutaneously into rabbits receiving systemic gentamicin. Ultrasound was applied for 24 h to one disk. Both disks were removed, and viable bacteria were counted. Pulsed ultrasound significantly reduced bacterial viability below that of nontreated biofilms without damage to the skin.

The evolution of vertebrate antigen receptors: a phylogenetic approach

Classical T cells, those with alpha beta T-cell receptors (TCRs), are an important component of the dominant paradigm for self-nonself immune recognition in vertebrates. alpha beta T cells recognize foreign peptide antigens when they are bound to MHC molecules on the surfaces of antigen-presenting cells. gamma delta T cells bear a similar receptor, and it is often assumed that these T cells also require specialized antigen-presenting molecules for immune recognition, which we term "indirect antigen recognition." B-cell receptors, or immunoglobulins, bind directly to antigens without the help of a specialized antigen-presenting molecule. Phylogenetically, it has been assumed that T-cell receptors and the genes that encode them are a monophyletic group, and that "indirect" antigen recognition evolved before the split into two types of TCR. Recently, however, it has been proposed that gamma delta-TCRs bind directly to antigens, as do immunoglobulins (Ig's). This calls into question the null hypothesis that indirect antigen recognition is a common characteristic of TCRs and, by extension, the hypothesis that all TCR gene sequences form a monophyletic group. To determine whether alternative explanations for antigen recognition and other historical relationships among TCR genes might be possible, we performed phylogenetic analyses on amino acid sequences of the constant and variable regions which encode the basic subunits of TCR and Ig molecules. We used both maximum-parsimony and genetic distance-based methods and could find no strong support for the hypothesis of TCR monophyly. Analyses of the constant region suggest that TCR gamma or delta sequences are the most ancient, implying that the ancestral immune cell was like a modern gamma delta T cell. From this gamma delta-like ancestor arose alpha beta T cells and B cells, implying that indirect antigen recognition is indeed a derived property of alpha beta-TCRs. Analyses of the variable regions are complicated by strong selection on antigen-binding sequences, but imply that direct antigen binding is the ancestral condition.

Microchimerism and scleroderma

It is now known that cells traffic between fetus and mother during normal human pregnancy. Moreover, fetal cells have been found to persist in the maternal peripheral blood for decades after childbirth. Chronic graft-versus-host disease, a known condition of chimerism that occurs after allogeneic hematopoietic stem cell transplantation has clinical similarities to some autoimmune diseases, including scleroderma (SSc). SSc has a predilection for women and an increased incidence in women following childbearing years. These observations when considered together with the longterm persistence of fetal cells led to the hypothesis that microchimerism is involved in autoimmune diseases such as SSc. Initial studies of women with SSc lend support to the hypothesis. Microchimerism, however, is also very common in healthy normals, and available data is not sufficient to be conclusive with respect to disease pathogenesis. Microchimerism can also occur due to engraftment from a blood transfusion, from a twin, or from the mother, sources that are applicable to men and women who have never been pregnant. The mechanism(s) by which microchimerism might contribute to SSc are not known, although some insight may be gained from studies of chimerism in transplantation biology. If microchimerism does contribute to the pathogenesis of autoimmune disorders such as SSc, it is likely that new therapeutic strategies could be developed.

Fetal microchimerism alone does not contribute to the induction of primary biliary cirrhosis

Microchimerism has been implicated in the etiology of autoimmune diseases. It has also been implicated in the induction/maintenance of fetal tolerance. We used polymerase chain reaction (PCR) analysis to determine whether microchimerism occurred in patients who subsequently developed primary biliary cirrhosis (PBC), and thus may be involved in its etiology. We performed PCR amplification of sequences unique to both the X and Y chromosomes from the livers of 37 women with PBC and 39 female controls using WAVE technology; a very sensitive technology based on an ion-pair reverse-phase high-performance liquid chromatography system. All patients were known to have had at least 1 son and it was confirmed that PBC was diagnosed after the birth of the son. Data were analyzed for both detection of the Y chromosome gene and the ratio of the yield of the Y chromosome PCR products to the X chromosome. The prevalence of Y chromosome detection in PBC was 26 of 37 (70%) compared with 28 of 39 (72%) in controls, and the ratio of Y chromosome to X chromosome was similar between the PBC and control groups, 0.402 +/- 0.143 vs. 0.271 +/- 0.055, respectively. Our results, using our more sensitive technology, showed that microchimerism is a very common event in human liver and supported the thesis that this may contribute to the induction/maintenance of fetal tolerance. However, although we cannot exclude the possibility that select fetal major histocompatibility complex (MHC) haplotypes might contribute to disease susceptibility, our data suggest that microchimerism by itself does not play a significant role in the development of PBC.