Changes of lymphocyte subsets in normal pregnant and postpartum women: postpartum increase in NK/K (Leu 7) cells

Innate and Adaptive Immune Systems in Physiological and Pathological Pregnancy

The dynamic immunological changes occurring throughout pregnancy are well-orchestrated and important for the success of the pregnancy. One of the key immune adaptations is the maternal immune tolerance towards the semi-allogeneic fetus. In this review, we provide a comprehensive overview of what is known about the innate and adaptive immunological changes in pregnancy and the role(s) of specific immune cells during physiological and pathological pregnancy. Alongside this, we provided details of remaining questions and challenges, as well as future perspectives for this growing field of research. Understanding the immunological changes that occur can inform potential strategies on treatments for the optimal health of the neonate and pregnant individual both during and after pregnancy.

Postpartum hepatitis and host immunity in pregnant women with chronic HBV infection

In order to develop immune tolerant to the fetal, maternal immune system will have some modification comparing to the time before pregnancy. Immune tolerance starts and develops at the maternal placental interface. In innate immunity, decidual natural killer (dNK) cells, macrophages and dendritic cells play a key role in immue tolerance. In adaptive immunity, a moderate increase of number and immune inhibition function of regulatory T cells (Treg) are essential for immune tolerance. The trophoblast cells and immune cells expressing indoleamine 2,3-dioxygenase (IDO), the trophoblast cells expressing HLA-G, and Th1/Th2 shifting to Th2 dominant and Th17/Treg shifting to Treg domiant are in favor of maternal fetal immune tolerance. Steroids (estrogen and progesterone) and human chorionic gonadotropin (HCG) also participate in immune tolerance by inducing Treg cells or upregulating immunosuppressive cytokines. Most of the patients with chronic HBV infection are in the "HBV immune tolerance period" before pregnancy, and the liver disease is relatively stable during pregnancy. In chronic HBV infection women, after delivery, the relative immunosuppression in vivo is reversed, and Th1 is dominant in Th1/Th2 and Th17 is dominant in Th17/Treg balance. After delivery, the number of Treg decrease and NK cells increase in quantity and cytotoxicity in peripheral blood. Liver NK cells may cause liver inflammation through a non-antigen specific mechanism. After delivery, the number of CD8⁺ T cells will increase and HBV specific T cell response recovers from the disfunction in pregnancy. Under the background of postpartum inflammation, the rapid decrease of cortisol after delivery, and especially the enhancement of HBV specific T cell response induced by HBV DNA and cytokines, are the main reasons for postpartum hepatitis. HBeAg positive, especially HBeAg<700 S/CO, and HBV DNA>3-5Log₁₀IU/ml are risk factors for postpartum hepatitis. Antiviral treatment in late pregnancy can reduce the incidence of mother to child transmission (MTCT) in chronic HBV infection women. Chronic HBV infection women have hepatitis both during pregnancy and more often in 12 weeks postpartum. It is generally agreed that postpartum hepatitis is mild symptoms and self-limited. Delaying drug withdrawal to 48 weeks can increase the seroconversion rate of HBeAg in delivery women with elevated alanine aminotransferase (ALT) in pregnancy.

Placenta-Derived Exosomes as a Modulator in Maternal Immune Tolerance During Pregnancy

Exosomes are a subset of extracellular vesicles with an average diameter of ~100nm. Exosomes are released by all cells through an endosome-dependent pathway and carry nucleic acids, proteins, lipids, cytokines and metabolites, mirroring the state of the originating cells. The function of exosomes has been implicated in various reproduction processes, such as embryo development, implantation, decidualization and placentation. Placenta-derived exosomes (pEXO) can be detected in the maternal blood as early as 6 weeks after conception and their levels increase with gestational age. Importantly, alternations in the molecular signatures of pEXO are observed in pregnancy-related complications. Thus, these differentially expressed molecules could be the potential biomarkers for diagnosis of the pregnancy-associated diseases. Recent studies have demonstrated that pEXO play a key role in the establishment of maternal immune tolerance, which is critical for a successful pregnancy. To gain a better understanding of the underlying mechanism, we highlighted the advanced studies of pEXO on immune cells in pregnancy.

Maternal Immunological Adaptation During Normal Pregnancy

The risk and severity of specific infections are increased during pregnancy due to a combination of physiological and immunological changes. Characterizing the maternal immune system during pregnancy is important to understand how the maternal immune system maintains tolerance towards the allogeneic fetus. This may also inform strategies to prevent maternal fatalities due to infections and optimize maternal vaccination to best protect the mother-fetus dyad and the infant after birth. In this review, we describe what is known about the immunological changes that occur during a normal pregnancy.

Reproductive immunomodulatory functions of B cells in pregnancy

Pregnancy, a challenging physiological state, requires shuffling of conventional immune work-sets. Strategies to tolerate the semi-allogenic fetus in normal human pregnancy are multivariate with perfect modulation of the immune cells. Pregnancy is marked by B cell lymphocytopenia accompanied by reduced responsiveness to infectious agents. Besides this old age concept, plenty of research confirms that B cells have other crucial roles in pregnancy and undergo a wide range of modifications in terms of its proliferation, switching between its subtypes, variation in antibody productions, shifting the tides of cytokines as well as regulating other immune cells. B cells establish tolerant environment in pregnancy by producing protective antibodies to encounter the foreign paternal antigens. Regulatory B cells (Bregs) have adopted anti-inflammatory characteristics to sustain normal pregnancy. Moreover, the colossal physiological alterations during human pregnancy also include synchronized changes in the cross-talks between the pregnancy hormones and B cells. These aspects of pregnancy from the view point of B cell functions have so far appeared individually in discrete reports. This review finds its novelty in concisely presenting every facet of association of B cell with human pregnancy.

Dynamics of leukocyte telomere length in pregnant women living with HIV, and HIV-negative pregnant women: A longitudinal observational study

Background

HIV-mediated inflammation and immune activation can accelerate telomere attrition. In addition, antiretrovirals can inhibit telomerase, possibly shortening telomeres. We examined the longitudinal dynamics of leukocyte telomere length (LTL) during pregnancy in a unique cohort of women living with HIV (WLWH) treated with combination antiretroviral therapy (cART), and HIV-negative control women.

Methods

Blood was collected at three visits during pregnancy, at 13–23, >23–30, and >30–40 weeks of gestation, and for WLWH only, at 6 weeks post-partum. LTL was measured by qPCR and both cross-sectional and longitudinal (MANOVA) models were used to examine possible predictors of LTL among participants who attended all three visits during pregnancy.

Results

Among WLWH (n = 64) and HIV-negative women (n = 41), within participant LTL were correlated throughout pregnancy (p<0.001). LTL was shorter among WLWH at first visit, but this difference waned by the second visit. WLWH who discontinued cART post-partum experienced a decrease in LTL. Longitudinally, LTL was similar in both groups and increased as gestation progressed, a change that was more pronounced among women under 35 years. Among WLWH, both smoking throughout pregnancy (p = 0.04) and receiving a ritonavir-boosted protease inhibitor-based regimen (p = 0.03) were independently associated with shorter LTL.

Conclusions

LTL increases as pregnancy progresses; the reasons for this are unknown but may relate to changes in blood volume, hormones, and/or cell subset distribution. While our observations need confirmation in an independent cohort, our data suggest that although some cART regimens may influence LTL, being on cART appears overall protective and that stopping cART post-partum may negatively impact LTL. The effect of smoking on LTL is clearly negative, stressing the importance of smoking cessation.

Serum markers of B-cell activation in pregnancy during late gestation, delivery, and the postpartum period

PROBLEM

B cells are vital for the normal evolution of pregnancy due to their humoral and possible regulatory activities. Our group and others have documented that circulating B-cell subsets undergo changes from normal late pregnancy to the postpartum period. However, the underlying mechanisms are poorly understood. Therefore, this study examined the degree of B-cell activation in normal pregnancy by analyzing the levels of serum markers in healthy pregnant women during the third trimester of pregnancy, the day of delivery, and the postpartum period.

METHOD OF STUDY

A prospective study including pregnant and non-pregnant women attending routine care was undertaken at a hospital clinic. Sociodemographic and clinical data were collected, along with peripheral blood samples. The serum levels of soluble CD23 (sCD23), B-cell-activating factor (BAFF), kappa (κ) and lambda (λ) free light chains (FLC), IgA, IgG, and IgM were quantified.

RESULTS

Our study included 43 third trimester pregnant and 35 non-pregnant women. In the pregnant women, the median levels of sCD23, BAFF, IgG, and κ FLC were significantly higher during the postpartum period than during the third trimester of pregnancy. Compared to the non-pregnant women, the third trimester pregnant women had higher median BAFF levels and lower sCD23, IgA, IgG, and FLC levels.

CONCLUSION

Changes in serum markers of B-cell kinetics that occur during pregnancy often persist into the postpartum period and affect the secretion of immunoglobulins from different classes. Further studies are needed to clarify the biological significance of our observations.

Are naïve T cells and class-switched memory (IgD- CD27+) B cells not essential for establishment and maintenance of pregnancy? Insights from a case of common variable immunodeficiency with pregnancy

The disruption of adaptive immune response has adverse effects on the establishment and maintenance of pregnancy. The adaptive immune system is regulated by several types of immune cells. However, there is limited information about cell hierarchy in the adaptive immune response to the establishment and maintenance of pregnancy in women. The assessment of the outcome of pregnancy in primary immunodeficiency diseases could help in understanding the cell hierarchy in the adaptive immune system during pregnancy. Common variable immunodeficiency (CVID) is a heterogeneous adaptive immune system disorder characterized by primary hypogammaglobulinemia. A few studies have previously reported the assessment of the T and B cell subpopulations in CVID patients. However, an assessment of the subpopulations of T and B cells and the outcome of pregnancy in women with CVID has not been reported till date. Most CVID patients show a general decrease in the expression of CD27 in B cells. The assessment of pregnancy and the subpopulations of T and B cells in CVID women with severe reduction in the naïve T and switched B cells could help understand whether these cells are essential for the establishment and maintenance of pregnancy in women.

Characterization of B cells in healthy pregnant women from late pregnancy to post-partum: a prospective observational study

Background

B cells play a role in pregnancy due to their humoral and regulatory activities. To our knowledge, different maturational stages (from transitional to memory) of circulating B cell subsets have not yet been characterized (cell quantification and phenotype identification) in healthy pregnant women. Thus, the objective of our study was to characterize these subsets (as well as regulatory B cells) from late pregnancy to post-partum and to compare them with the circulating B cells of non-pregnant women.

Methods

In all of the enrolled women, flow cytometry was used to characterize the circulating B cell subsets according to the expression of IgD and CD38 (Bm1-Bm5 classification system). Regulatory B cells were characterized based on the expression of surface antigens (CD24, CD27, and CD38) and the production of IL-10 after lipopolysaccharide stimulation.

Results

Compared to the absolute counts of B cells in the non-pregnant women (n = 35), those in the pregnant women (n = 43) were significantly lower (p < 0.05) during the 3rd trimester of pregnancy and on delivery day (immediately after delivery). The percentages of these cells on delivery day and at post-partum were significantly lower than those in the non-pregnant women.

In general, the absolute counts and percentages of the majority of the B cell subsets were significantly lower in the 3rd trimester of pregnancy and on delivery day than in the non-pregnant women. However, these counts and percentages did not differ significantly between the post-partum and the non-pregnant women.

The most notable exceptions to the above were the percentages of naïve B cells (which were significantly higher in the 3rd trimester and on delivery day than in the non-pregnant women) and of CD24^hiCD38^hi regulatory B cells (which were significantly higher in the post-partum than in the non-pregnant women).

Conclusion

According to our study, the peripheral B cell compartment undergoes quantitative changes during normal late pregnancy and post-partum. Such findings may allow us to better understand immunomodulation during human pregnancy and provide evidence that could aid in the development of new strategies to diagnose and treat pregnancy-associated disturbances. Our findings could also be useful for studies of the mechanisms of maternal responses to vaccination and infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-016-0927-7) contains supplementary material, which is available to authorized users.

Maternal vaccination: moving the science forward

BACKGROUND

Infections remain one of the leading causes of morbidity in pregnant women and newborns, with vaccine-preventable infections contributing significantly to the burden of disease. In the past decade, maternal vaccination has emerged as a promising public health strategy to prevent and combat maternal, fetal and neonatal infections. Despite a number of universally recommended maternal vaccines, the development and evaluation of safe and effective maternal vaccines and their wide acceptance are hampered by the lack of thorough understanding of the efficacy and safety in the pregnant women and the offspring.

METHODS

An outline was synthesized based on the current status and major gaps in the knowledge of maternal vaccination. A systematic literature search in PUBMED was undertaken using the key words in each section title of the outline to retrieve articles relevant to pregnancy. Articles cited were selected based on relevance and quality. On the basis of the reviewed information, a perspective on the future directions of maternal vaccination research was formulated.

RESULTS

Maternal vaccination can generate active immune protection in the mother and elicit systemic immunoglobulin G (IgG) and mucosal IgG, IgA and IgM responses to confer neonatal protection. The maternal immune system undergoes significant modulation during pregnancy, which influences responsiveness to vaccines. Significant gaps exist in our knowledge of the efficacy and safety of maternal vaccines, and no maternal vaccines against a large number of old and emerging pathogens are available. Public acceptance of maternal vaccination has been low.

CONCLUSIONS

To tackle the scientific challenges of maternal vaccination and to provide the public with informed vaccination choices, scientists and clinicians in different disciplines must work closely and have a mechanistic understanding of the systemic, reproductive and mammary mucosal immune responses to vaccines. The use of animal models should be coupled with human studies in an iterative manner for maternal vaccine experimentation, evaluation and optimization. Systems biology approaches should be adopted to improve the speed, accuracy and safety of maternal vaccine targeting.

To B or not to B cells-mediate a healthy start to life

Maternal immune responses during pregnancy are critical in programming the future health of a newborn. The maternal immune system is required to accommodate fetal immune tolerance as well as to provide a protective defence against infections for the immunocompromised mother and her baby during gestation and lactation. Natural immunity and antibody production by maternal B cells play a significant role in providing such immunoprotection. However, aberrations in the B cell compartment as a consequence of maternal autoimmunity can pose serious risks to both the mother and her baby. Despite their potential implication in shaping pregnancy outcomes, the role of B cells in human pregnancy has been poorly studied. This review focuses on the role of B cells and the implications of B cell depletion therapy in pregnancy. It highlights the evidence of an association between aberrant B cell compartment and obstetric conditions. It also alludes to the potential mechanisms that amplify these B cell aberrances and thereby contribute to exacerbation of some maternal autoimmune conditions and poor neonatal outcomes. Clinical and experimental evidence suggests strongly that maternal autoantibodies contribute directly to the pathologies of obstetric and neonatal conditions that have significant implications for the lifelong health of a newborn. The evidence for clinical benefit and safety of B cell depletion therapies in pregnancy is reviewed, and an argument is mounted for further clinical evaluation of B cell-targeted therapies in high-risk pregnancy, with an emphasis on improving neonatal outcomes and prevention of neonatal conditions such as congenital heart block and fetal/neonatal alloimmune thrombocytopenia.

Cryptococcal meningitis in HIV negative pregnant women: case report and review of literature

INTRODUCTION

Cryptococcosis has become an important entity due to the epidemic of AIDS and therefore it is a significant opportunistic infection. However, there are case reports of cryptococcal meningitis in immune competent pregnant women. Since pregnancy is considered a period of relative immunosuppression, which likely prevents fetal rejection, this could explain the occurrence of opportunistic infections.

OBJECTIVE

To report a case of cryptococcosis, and review all cases involving pregnancy and neurocryptococcal infection in immune competent pregnant patients.

METHODS

Case report and systematic review of the literature using the MEDLINE and SciELO databases.

DISCUSSION

A total of 27 patients were analyzed from 19 studies. The mean age at diagnosis was 26.4 years. There were six patients in their first trimester of pregnancy, 10 in the second, eight in the third and three post-partum. The most prevalent symptoms were headache (85.2%), altered vision (44.4%), altered mental status (44.4%), nausea (40.7%) and fever (33.3%). There were nine deaths (33.3%). Most of the patients received intravenous amphotericin B as treatment (77.8%). The majority (66.6%) of the patients accomplished a term delivery with healthy infants.

CONCLUSION

Cryptococcal meningitis should be considered during pregnancy in cases of unexplained headache, altered vision, altered mental status, nausea and fever. Patients with a confirmed diagnosis should be admitted and treated with amphotericin B.

Postpartum increase of serum thioredoxin concentrations and the relation to CD8 lymphocytes

BACKGROUND

There are few data on oxidative stresses during and after pregnancy, although aggravation of autoimmune disease is implicated in oxidative stress and occurs frequently in the postpartum period. Thioredoxin (TRX) is a stress-inducible protein, and is used as a good biomarker for oxidative stress. To clarify the changes in the levels of oxidative stress during and after pregnancy, we examined serum TRX levels and the numbers of lymphocyte subsets.

METHODS

We measured serum TRX levels by enzyme-linked immunosorbent assay (ELISA), and neutrophils, lymphocytes, and CD4 and CD8 lymphocytes by flow cytometry in peripheral blood from 88 healthy pregnant women, 26 just after delivery women, 77 healthy postpartum women and 19 healthy non-pregnant women.

RESULTS

The serum levels of TRX did not change during pregnancy, but increased in four, seven and 10 months postpartum. Serum TRX levels were correlated with the percentages of neutrophils in normal non-pregnant women and women one month postpartum, and with those of CD8 lymphocytes in early pregnant women and women one and four months postpartum.

CONCLUSIONS

Oxidative stress increased in the postpartum period, and the levels at one and four months postpartum were related to CD8 lymphocytes.

Effects of Bacillus cereus var. toyoi on immune parameters of pregnant sows

Changing immune parameters during pregnancy have previously been reported in humans and cattle, and have been suggested to contribute to increased susceptibility to infections. However, data regarding immune parameters during pregnancy in sows are rare. In this study, we investigated the peripartal immune status of sows using phenotypical (FACS analysis) as well as functional (proliferation assays, cytokine analysis) parameters of peripheral blood mononuclear cells (PBMCs) in pregnant sows. In previous studies, we reported a modulation of the immune system after feed supplementation of the probiotic Bacillus cereus var. toyoi in piglets [Schierack, P., Wieler, L.H., Taras, D., Herwig, V., Tachu, B., Hlinak, A., Schmidt, M.F., Scharek, L., 2007. Bacillus cereus var. toyoi enhanced systemic immune response in piglets. Vet. Immunol. Immunopathol. 118, 1-11]. Here, we extended these previous studies to include investigations of possible probiotic effects on the peripartal immune status of sows and their reproductivity. We show that immune parameters of sows change during pregnancy, the proliferative response of PBMCs to several bacterial antigens in control animals decreased from days 90 to 30 ante partum. Relative numbers (%) of CD3+CD8+, CD4+, cytotoxic T, CD14+ and CD21+ cells were reduced compared to non-pregnant sows. In contrast, the proliferative response of PBMCs of probiotic-treated sows increased during pregnancy. Bacterial antigens primarily stimulated the proliferation of naïve CD21+ cells and the relative CD21+ cell numbers were elevated in the probiotic group in the absence of effects on other immune cell populations. The clinical and microbial status of both control and probiotic sows was similar, excluding pre-existing health problems or infections as responsible for the immunological changes, and feed supplementation also had no significant effects on reproductivity. The results suggest that the probiotic B. cereus var. toyoi can alter the proliferative response of lymphocytes and affects the immune cell population ratios of pregnant sows. How and to what extent this may affect health and reproductivity should be the focus of further studies.

Activation of CD8+ regulatory T cells by human placental trophoblasts

The immunological basis by which a mother tolerates her semi-allogeneic fetus remains poorly understood. Several mechanisms are likely to contribute to this phenomenon including active immune regulation by regulatory T cells. In this article, we report that human placental trophoblasts activate a clonal population of CD8(+) T cells with regulatory function. These cells are not MHC class I restricted, but require costimulation through a member of the carcinoembryonic Ag family present on early gestation trophoblasts. These regulatory T cells express the mucosal markers CD101 and CD103 and display selective usage of the TCR gene Vbeta9. CD8(+) T cells isolated from the peripheral blood of pregnant mothers (16-28 wk) also demonstrate expansions in the same Vbeta family (Vbeta9), signaling a possible role for these cells in preventing fetal rejection in vivo. We have previously characterized a subset of CD8(+) regulatory T cells activated by the combination of the nonclassical class I molecule CD1d and a costimulatory molecule of the carcinoembryonic Ag family present on the intestinal epithelium. These data support the concept that distinct regulatory T cell populations exist at different sites and may be regulated locally by unique restriction elements, costimulatory signals, and Ags.

Effects of prophylactic thyroid hormone replacement in euthyroid Hashimoto's thyroiditis

Hashimoto's thyroiditis is the most frequent autoimmune thyroid disease. L-thyroxine therapy can reduce the incidence and alleviate the symptoms of this disease. The aim of this study was to evaluate the effects of prophylactic L-thyroxine treatment on clinical and laboratory findings of patients who were euthyroid at the time of diagnosis. Thirty-three patients who had diagnosis of euthyroid Hashimoto's thyroiditis were randomized to two groups, one group received prophylactic L-thyroxine treatment and the other was followed-up without treatment. Initial thyroid function tests, autoantibodies, ultrasonography, fine needle aspiration biopsy and peripheral blood lymphocyte subsets were similar in the two study groups. After 15 months of L-thyroxine treatment, there was a significant increase in free T4 and a significant decrease in TSH and anti-thyroglobulin antibody anti-thyroid peroxidase antibody levels. CD8+ cell counts increased in both groups, CD4/CD8 levels decreased significantly because of the increase in CD8+ cell count levels. Though there was no change in cytological findings, ultrasonography showed a decrease in thyroid volume in L-thyroxine receiving patients whereas an increase was detected in patients who were followed without treatment. In conclusion, prophylactic thyroid hormone therapy can be used in patients with Hashimoto's thyroiditis even if they are euthyroid.

Thyroid disorders associated with pregnancy: etiology, diagnosis, and management

Pregnancy has an effect on thyroid economy with significant changes in iodine metabolism, serum thyroid binding proteins, and the development of maternal goiter especially in iodine-deficient areas. Pregnancy is also accompanied by immunologic changes, mainly characterized by a shift from a T helper-1 (Th1) lymphocyte to a Th2 lymphocyte state. Thyroid peroxidase antibodies are present in 10% of women at 14 weeks' gestation, and are associated with (i) an increased pregnancy failure (i.e. abortion), (ii) an increased incidence of gestational thyroid dysfunction, and (iii) a predisposition to postpartum thyroiditis. Thyroid function should be measured in women with severe hyperemesis gravidarum but not in every patient with nausea and vomiting during pregnancy. Graves hyperthyroidism during pregnancy is best managed with propylthiouracil administered throughout gestation. Thyroid-stimulating hormone-receptor antibody measurements at 36 weeks' gestation are predictive of transient neonatal hyperthyroidism, and should be checked even in previously treated patients receiving thyroxine. Postpartum exacerbation of hyperthyroidism is common, and should be evaluated in women with Graves disease not on treatment. Radioiodine therapy in pregnancy is absolutely contraindicated. Hypothyroidism (including subclinical hypothyroidism) occurs in about 2.5% of pregnancies, and may lead to obstetric and neonatal complications as well as being a cause of infertility. During the last few decades, evidence has been presented to underpin the critical importance of adequate fetal thyroid hormone levels in order to ensure normal central and peripheral nervous system maturation. In iodine-deficient and iodine-sufficient areas, low maternal circulating thyroxine levels have been associated with a significant decrement in child IQ and development. These data suggest the advisability of further evaluation for a screening program early in pregnancy to identify women with hypothyroxinemia, and the initiation of prompt treatment for its correction. Hypothyroidism in pregnancy is treated with a larger dose of thyroxine than in the nonpregnant state. Postpartum thyroid dysfunction (PPTD) occurs in 50% of women found to have thyroid peroxidase antibodies in early pregnancy. The hypothyroid phase of PPTD is symptomatic and requires thyroxine therapy. A high incidence (25-30%) of permanent hypothyroidism has been noted in these women. Women having transient PPTD with hypothyroidism should be monitored frequently, as there is a 50% chance of these patients developing hypothyroidism during the next 7 years.

Changes in peripheral leukocyte subsets in dairy cows with inflammatory diseases after calving

To clarify the cellular immune system in dairy cows with inflammatory diseases after calving, the leukocyte subsets were examined in Holstein dairy cows. Twenty Holstein cows reared in one herd, were used in this study. Nine cows (Group 1) experienced onset of mastitis or puerperal fever within 2 weeks after calving, and the other eleven cows remained healthy (Group 2) after calving. The numbers of CD3(+), CD4(+) and CD8(+) cells tended to be lower in Group 1 than in Group 2 from the day of calving through week 1. These results suggested that the cows with inflammatory diseases might have experienced a decline in T cells by the day of calving, before the onset of disease.

Severe autoimmune hepatitis first presenting in the early post partum period

BACKGROUND & AIMS

Autoimmune hepatitis (AIH) may run an aggressive clinical course if untreated. The influence of pregnancy on AIH is variable. Both flares in disease activity and remissions, often followed by a post partum flare, are well recognized. In contrast, definite AIH first presenting in the early post partum period has not been reported.

METHODS

We discuss a case series of 5 patients who developed severe AIH within 4 months post partum.

RESULTS

The diagnosis of AIH was definite based on internationally accepted criteria. Liver injury responded to conventional immunosuppressive therapy in all patients. Immune reactivation in the early post partum period may contribute to this entity.

CONCLUSIONS

AIH should be considered in the differential diagnosis of liver dysfunction first presenting in the early post partum period.

HIV-1: maternal prognosis

Profound modifications in the profile of patients are currently being observed within the epidemic context of AIDS, especially with respect to pauperization and feminization of the disease. The population most frequently affected is in the reproductive age, and among adults aged 18 to 24 years, the ratio is 1 man to 1 woman, a phenomenon occurring uniformly all over the world. One of the main challenges for HIV-1-infected pregnant women and their doctors is the effect of the interaction between HIV infection and pregnancy. The present article is a review of the literature; and its objective is to assess the influence of HIV-1 infection seen from the maternal perspective, with a discussion of immunologic function, maternal prognosis, and the HIV-abortion interface. At present, we cannot conclude that pregnancy has a short-term effect on the evolution of HIV infection, but the concomitance of HIV and pregnancy may adversely affect the prognosis of gestation, especially in view of its frequent association with increased abortion and puerperal morbidity rates.

Clinical course of psoriasis during pregnancy

BACKGROUND

Since the landmark study on rheumatoid arthritis, many reports have suggested that physiological changes during pregnancy often induce remission of systemic and cutaneous inflammatory diseases. In this study we investigated the clinical course of psoriasis during pregnancy.

OBJECTIVE

In this retrospective study information was collected from Psoriasis Life History Questionnaires. The data obtained from 736 questionnaires were entered into a computerized database. Information relevant to the clinical course of psoriasis during pregnancy was evaluated in respect to improvement/worsening, number of pregnancies, severity of the disease, and certain other clinical parameters.

RESULTS

In a majority of the patients psoriasis improved during pregnancy. Data available from 91 pregnancies revealed: psoriasis improved in 51 (56%), worsened in 24 (26.4%), and remained unchanged in 16 (17.6%). Also, appearance of psoriasis new lesions was found to be frequent during the early postpartum period. Patients who improved in the first pregnancy were found to have a similar response in the following pregnancies.

CONCLUSION

Research on immuno-endocrine interactions during pregnancy is a relatively new field. Proinflammatory Th-1 cytokines are up-regulated in psoriasis and play a key role in the inflammatory cascades of psoriasis. It is likely that during pregnancy the Th-2 cytokine-mediated down-regulation of the immune response by virtue of its anti-inflammatory and antagonizing effects on the Th-1 cytokines improves psoriasis.

Thyroid disease in relation to pregnancy: a decade of change

Inspection of the references cited in this review indicates that much work has occurred in the area of thyroid and pregnancy during the last decade. Significant advances in our understanding of the immunology of pregnancy and the effect of thyroid disease on this process have taken place. The role of hCG in the physiology of pregnancy and its relevance to thyroid function has been an emerging theme. There is still no clear explanation for the association between thyroid antibodies and infertility or miscarriage. During the last decade a general concensus has developed in relation to the management of hyperthyroidism in pregnancy although there are still variations in antithyroid drug use at this time. The aetiological classification of congenital hyper- and hypothyroidism utilizing new technologies has opened up a new perspective on these disorders. Attention has been drawn to the importance of treating maternal hypothyroidism with adequate thyroid replacement therapy and to the possibility of impaired child neuropsychological development consequent on low maternal thyroid hormone concentration in early gestation in non iodine deficient areas. Significant advances have been made during the last decade in the description of the clinical features and in our understanding of the pathogenesis of postpartum thyroid disease. The importance of long-term follow up of selected patient groups has also been emphasized.

Effect of beta-carotene supplementation and lactation on carotenoid metabolism and mitogenic T lymphocyte proliferation

BACKGROUND

Information is lacking regarding the effects of beta-carotene supplementation, early lactation, or both on circulating carotenoid concentrations and T lymphocyte proliferation.

OBJECTIVES

This study investigated the effects of short-term beta-carotene supplementation (30 mg/d for 28 d) during early lactation (days 4-32 postpartum) on circulating carotenoid concentrations and on the T lymphocyte proliferative response to phytohemagglutinin.

DESIGN

Subjects aged 19-39 y were paired [lactating (4 d postpartum) and nonlactating (never pregnant, healthy women)] and randomly assigned to receive either beta-carotene or a placebo. During the study, subjects provided eight 24-h food records for analysis with the NUTRITIONIST IV and US Department of Agriculture carotenoid databases. Nonfasting blood samples were collected at baseline and at 28 d. Plasma analysis included quantification of alpha-carotene, beta-carotene, lutein, lycopene, retinol, and alpha-tocopherol, complete differential blood cell counts, and lymphocyte proliferative activity.

RESULTS

beta-Carotene supplementation increased beta-carotene (P < 0.001) and alpha-carotene (P < 0.05) concentrations but did not affect lycopene concentrations significantly. Supplemented women showed significant decreases in plasma lutein (P < 0.03), as did lactating subjects (P < 0.02). Neither lactation nor beta-carotene supplementation affected the T lymphocyte proliferative response to phytohemagglutinin.

CONCLUSIONS

Our results suggest that beta-carotene supplementation as well as some events related to parturition, initiation of lactation, or both alter circulating concentrations of lutein. beta-Carotene supplementation does not enhance T lymphocyte immune competence in healthy women.

The thyroid immunology of the postpartum period

Autoimmune thyroid disease (AITD) is suppressed during pregnancy and is exacerbated in the postpartum period. Studies indicate that new-onset AITD occurs in up to 10% of all women in the postpartum period and that up to 60% of Graves' patients in the reproductive years give a history of postpartum onset. Despite this extraordinary epidemiological evidence, the causes of these exacerbations are uncertain and have yet to be adequately investigated. Explaining these postpartum changes, therefore, remains hypothetical. Mechanisms invoked include the passage of fetal cells to the mother during pregnancy establishing maternal microchimerism, pregnancy-induced changes in the thyroid gland itself, and the role of prolactin as a consequence of breast-feeding. Once the disease onset or exacerbation, is established, then there have been considerable advances in our understanding of the immunopathology. Thyroid cell destruction (via apoptosis) or activation (via thyrotropin [TSH] receptor autoantibody induction) appear to be similar to nonpostpartum-related disease. The reasons for the transience in postpartum disease, particularly thyroiditis, is likely to be related to the induction of clonal suicide and the mechanisms for this phenomenon are beginning to be explored. While we have a number of clinical indicators that allow us to predict postpartum thyroid disease (such as autoantibody titers), at present, we have no treatment to prevent the disease. Furthermore, our predictions are not helpful in a high enough proportion of the population to warrant screening of all women before delivery. At this time, the best clinical approach is watchful waiting and postpartum thyroid function testing where suspected.

A change from stimulatory to blocking antibody activity in Graves' disease during pregnancy

Remission of Graves' disease (GD) during pregnancy with recrudescence after delivery is commonly observed. However, as pregnancy is associated with type 2 rather than type 1 cytokine production, a decrease in thyroid-stimulating antibody (TSAb) activity alone is unlikely to account for the remission during pregnancy. We hypothesized that a change in the antibody characteristics may occur as pregnancy advances. Fifteen women were studied in the first, second, and third trimesters of pregnancy and 4 months postpartum. TSH receptor antibodies were determined using human thyroid cell cultures, and lymphocyte subsets were measured by flow cytometry. Median TSAb (determined by cAMP release) decreased from 280% (96-3200) to 130% (range, 35-350; P < 0.05) during pregnancy, but no significant change was noted with the TSH binding inhibitory antibody (TBII; determined by RRA). Thyroid stimulation-blocking antibody (TSBAb; inhibition of TSH-stimulated cAMP release) increased from 16 +/- 9% to 43 +/- 16% (mean +/- SD; P < 0.005). The increase in TSBAb was observed even among those patients who were in clinical remission before pregnancy. Overall, a negative correlation was observed between TSBAb activities and free T4 levels during pregnancy (r = -0.279; P < 0.05). Reciprocal changes in TSAb, TBII, and TSBAb levels were observed in the seven patients who relapsed during the postpartum period. In comparison, the healthy pregnant women (n = 14) were all negative for TSAb, TBII, and TSBAb throughout pregnancy. The absolute number of T lymphocytes, T helper cells, and natural killer cells, but not B cells, decreased significantly during pregnancy in both healthy women and GD patients. GD patients had significantly more CD5+ B cells at all stages of pregnancy compared to controls. In conclusion, a change in specificity from stimulatory to blocking antibodies was observed in GD patients during pregnancy and may contribute to the remission of GD during pregnancy.

Prevention and treatment of postpartum Graves' disease

Postpartum Graves' disease requires differentiation from postpartum thyroiditis and subacute thyroiditis in addition to other causes of hyperthyroidism. This may be done by assessing thyrotropin receptor antibody and radioiodine uptake together with clinical examination and thyroid scanning. The effect of pregnancy on thyroid function causes changes in iodine metabolism, thyroid hormone transport proteins and thyroid gland size. Amelioration of autoimmune disease such as Graves' disease, systemic lupus erythematosus and rheumatoid arthritis is often observed during pregnancy followed by postpartum exacerbation. The immunological effects of pregnancy involve placental factors as well as a transient diversion from T helper (Th) 1 to Th2 T-cell cytokine profile in addition to a change in B-cell lymphopoiesis. Prevention of postpartum Graves' disease by immune strategies which have been experimentally performed to reduce expression of diabetes in the non-obese diabetic mouse are attractive but not currently feasible in humans. Treatment of Graves' disease prior to pregnancy or postpartum with 131I is effective. Therapy with anti-thyroid drugs with or without thyroxine is variably effective.

Changes in T, B, and NK lymphocyte subsets during and after normal pregnancy

PROBLEM

Pregnancy affects the maternal immune system and the clinical course of maternal diseases. Here we report the changes in the detailed lymphocyte subsets of helper T cells, suppressor T cells, CD5+ B cells, T cell receptor (TCR) alpha beta-positive T cells (T alpha beta cells), TCR alpha beta-negative T cell (T gamma delta cells), and other during and after pregnancy through to one year postpartum, and discuss the significance of the changes.

METHOD

The absolute numbers of helper T cells, suppressor T cells, cytotoxic T cells, TCR alpha beta-negative T cells (T gamma delta cells), CD5- B cells, CD5+ B cells, and NK cell subsets were examined by two-color flow cytometry in peripheral blood from 51 healthy non-pregnant women, 106 healthy pregnant women, and 148 healthy postpartum women.

RESULTS

In early pregnancy, the numbers of suppressor T cells and NK cells with strong cytotoxicity (NK+3 cells) increased, and the number of cytotoxic T cells decreased. In late pregnancy, the helper T cell and NK+3 cell numbers decreased. T alpha beta, CD5- B and CD5+ B cells decreased during pregnancy. After delivery, helper T cells and cytotoxic T cells increased from 1 to 4 months postpartum, and suppressor T cells increased at 7 months postpartum. TCR alpha beta-negative T cells increased at 4 to 10 months postpartum. Both CD5- and CD5+ B cells decreased further at 1 month postpartum, but CD5+ B cells increased markedly at 7 to 10 months postpartum.

CONCLUSIONS

These data indicate that 1) early increases of suppressor T cells and NK+3 cells during pregnancy may be related to the mechanism to accept or reject the fetus in early pregnancy, respectively; 2) late decreases of helper T cells and NK+3 cells may be related to the maintenance of pregnancy: 3) postpartum increases of helper T cells, cytotoxic T cells, TCR alpha beta-negative T cells (T gamma delta cells), and CD5+ B cells may be related to the postpartum aggravation of autoimmune diseases; and 4) the immunological effects of pregnancy remains until about 1 year after delivery.

Lymphocyte, monocyte, and natural killer cell reference ranges in postpartal women

Normative values for immune-cell subsets in postpartal women, who are recovering from the relative immunosuppression of pregnancy, have not been established. Considerable differences in normative values for subsets of immune cells have been demonstrated based on sociodemographic factors, such as age and race. In order to make accurate clinical decisions about postpartal women, comparisons with normal reference ranges are necessary. Therefore, flow cytometric data for 51 healthy women at 4 months postpartum are presented and changes over the first 4 postpartal months are documented. The levels of some lymphocyte cell subsets, such as CD4+/CD45RA+ and Ia on lymphocytes, remained stable over time. The levels of other lymphocyte cell subsets, such as CD4+/CD29+, increased over the first 4 postpartal months, while those of other cell subsets, such as CD8 and CD11b, increased between delivery and 2 months postpartum and then dropped again by the fourth postpartal month. The levels of two natural killer cell subsets (CD3-/CD16+ and CD3-/CD57+) rose from delivery until 1 month postpartum and then plateaued. Comparisons were made with reference ranges of nonpostpartal groups provided in the literature and in a study of healthy women being conducted in the same laboratory, and postpartal women were found to have lower values of CD8, CD3-/CD16+, CD4+/CD45RA+, CD20, and CD11b than those reported in the literature.

Changes in soluble CD4 and CD8 proteins in healthy pregnant and postpartum women

PROBLEM

We examined physiological changes in serum levels of soluble CD4 (sCD4) and soluble CD8 (sCD8) during pregnancy and 1-12 months postpartum to study changes in the maternal immune system during and after pregnancy.

METHOD

The serum concentrations of sCD4 and sCD8 were measured by enzyme immunoassay in the sera separated from blood samples withdrawn from healthy women in the 1st, 2nd, and 3rd trimesters of pregnancy and 1, 4, 7, and 10-12 months postpartum (n = 182) and healthy non-pregnant women (n = 25), and in 90 of the women, the changes in sCD4 and sCD8 were compared with changes in the number of peripheral CD4+ and CD8+ cells measured by flow cytometry.

RESULTS

The serum concentration of sCD4 decreased throughout pregnancy, from the first trimester, and recovered gradually after delivery. The serum concentration of sCD8 did not change significantly during or after pregnancy compared to the concentration in the non-pregnant controls, but the concentration 1 month postpartum was significantly higher than that in the 3rd trimester. The number of CD4+ and cd8+ cells decreased during pregnancy but did not change significantly after delivery. Interestingly, the ratio of the serum sCD4 level to the number of CD4+ cells decreased and the ratio of the sCD8 level to the number of CD8+ cells increased in the first and second trimesters of pregnancy, but these ratios were within the normal range from the third trimester of pregnancy to 10-12 months postpartum.

CONCLUSIONS

Decreases in serum sCD4 concentration and in the ratio sCD4/CD4+ cells, and an increase in the ratio sCD8/CD8+ cells may be important factors in the immunological changes that occur during pregnancy.

In vitro cytotoxic activity of equine lymphocytes on equine herpesvirus-1 infected allogenic fibroblasts

The objectives of this study were to: (1) develop a technique to analyze the in vitro cytotoxic activity of lymphocytes from adult horses against equine herpesvirus-1 (EHV-1) infected allogenic equine dermal fibroblasts (EDF); (2) evaluate the ability of a 72-h in vitro incubation with interleukin-2 (IL-2) to enhance the lymphocytic cytolytic activity against EHV-1 infected EDF; (3) compare the cytotoxic activity of lymphocytes isolated from pregnant mares and non-pregnant mares against EHV-1 infected EDF; (4) ascertain if any correlations existed between the percent cytotoxicity and percentage of lymphocytes phenotypically identified by five different mouse-anti-equine monoclonal antibodies; and (5) determine if any correlation existed between virus-neutralizing antibody titers and the percent cytotoxicity. Results of the study indicate that in vitro cytotoxic activity of equine lymphocytes against EHV-1 infected allogenic fibroblasts can be measured with a standard 4-h 51Cr release assay. This activity was enhanced by an in vitro incubation with IL-2. The cytolytic activity of freshly isolated lymphocytes was greater for non-pregnant than pregnant mares. However, after IL-2 stimulation the cytolytic activity was greater for lymphocytes from pregnant mares. A positive correlation was not detected between the percentage of phenotypically identified cells and the percent cytotoxicity, although several negative correlations were present. This suggests that the cytotoxic activity was either not mediated by any of the phenotypically identified cell populations or that the activity was

Enhancement of the expression of progesterone receptor on progesterone-treated lymphocytes after immunotherapy in unexplained recurrent spontaneous abortion

PROBLEM

The immunological mechanism of an effective immunotherapy with paternal lymphocytes for unexplained recurrent spontaneous abortion (RSA) is not yet clear. Previous studies revealed that progesterone plays an important role in maintaining normal pregnancy and lower expression of progesterone receptor (PGR) on lymphocytes was found in RSA. Therefore, it was of interest to investigate whether immunotherapy for RSA would be able to enhance the expression of PGR on lymphocytes of RSA.

METHOD

PGR expression on lymphocytes was analyzed with indirect immunofluorescence using flow cytometry.

RESULTS

There was no change of PGR expression on PBL of RSA between pre- and post-immunotherapy (P > 0.05), while in the presence of 10.0 micrograms/ml progesterone for 24 h, PGR expressed on PBL on post-immunotherapy was increased significantly as compared with that of pre-immunotherapy in successful cases (P < 0.05) and decreased in abortive cases (P < 0.05). Most PGR was expressed on both CD4+ and CD8+ lymphocyte subsets. In successful cases, CD8+PGR+ subset of post-immunotherapy was found to be increased significantly (P < 0.05) in comparison with that of pre-immunotherapy.

CONCLUSION

The data in the present study suggest that immunotherapy for RSA induced a higher expression of PGR on progesterone-treated lymphocytes, which may be involved in successful pregnancy.

Relationship between serum prolactin, lactation and changes in maternal blood B-cell (CD19+) percents during the first 8 months post-partum

Lactation is an immunologically unique state when immune factors are produced by the mother for the protection of the infant rather than the mother. While several studies have focused on the immunological composition of human milk, much less information is available on maternal immune status during lactation. Sixty-four lactating and 43 bottle-feeding women at 1-2 weeks, 1, 2, 4 or 8 months post-partum were studied in a cross-sectional design, with 14 nulliparous women as controls. Flow cytometry analysis of peripheral blood lymphocytes showed dynamic, post-partum changes in the B-cell subpopulation. Among lactating women, the relative percents of CD19+ B-cells were significantly lower (P < 0.05) than control levels at 1-2 weeks and 1 month post-partum, but showed a significant, polynomial-linear rise (P < 0.05) over time, reaching control values by 2-4 months post-partum. Bottle-feeding women had an earlier rise in the percentage of CD19+ cells, with relative percents always significantly higher than their lactating counterparts. The differing patterns may be due to changes in serum prolactin concentrations because, among the post-partum women, relative percents of CD19+ cells were negatively correlated with baseline serum prolactin concentrations. These results have implications for maternal immunization programs designed to enhance maternal and/or infant well-being as well as other maternal health effects related to breastfeeding.

Psoriasis and pregnancy: hormone and immune system interaction

BACKGROUND

Various hormonal states are known to be associated with the waxing and waning of psoriasis. Patients with psoriasis commonly experience changes in their cutaneous disease during pregnancy or post partum.

OBJECTIVE

We evaluated 100 women with psoriasis by questionnaire and interview. The women had been seen at the Baylor Psoriasis Center, Dallas, and had experienced a pregnancy while having psoriasis. The answers were sorted and tabulated. In addition, we reviewed the literature to ascertain possible causes of clinical changes in psoriasis during pregnancy.

RESULTS

Ninety questionnaires were completed. Sixty-nine women (76.7%) described a change in their psoriasis during pregnancy with 57 (63.3%) noting improvement. Seventy-nine patients (87.7%) had a postpartum flare, most within 4 months of delivery.

CONCLUSIONS

The majority of women with psoriasis, who become pregnant, experience a change, usually an improvement, in their cutaneous disease. Pregnancy is associated with hormonal changes in estrogens and progesterone resulting in a state of altered immune surveillance.

Decreases in alpha beta T cell receptor negative T cells and CD8 cells, and an increase in CD4+ CD8+ cells in active Hashimoto's disease and subacute thyroiditis

We examined peripheral lymphocyte subsets in patients with autoimmune thyroid disease, or subacute thyroiditis, in the active stage when possible. During destructive thyrotoxicosis arising from alpha beta T cell receptor (TCR) negative T (WT31-CD3+) cells and CD8 (CD4-CD8+) cells decreased and those of CD4+CD8+ cells increased slightly, resulting in proportional increases in CD4 (CD4+CD8-) cells, non-T, non-B (CD5-CD19-) cells, and the CD4/CD8 cell ratio. Changes were similar in active subacute thyroiditis. During stimulative thyrotoxicosis in active Graves' disease, the numbers of such T lymphocyte subsets were not changed, but only the number of CD5+ B (CD5+CD19+) cells increased markedly, resulting in proportional decreases in total T (CD3+) cells, alpha beta+ TCR T (WT31+CD3+) cells, CD8 cells, and non-T, non-B cells. A serial study of some of the patients showed opposite changes in alpha beta TCR- T cells, the CD4/CD8 cell ratio, and CD5+ B cells between the active stages of Graves' and Hashimoto's diseases. alpha beta TCR- T cells were mostly gamma delta TCR+ T (IIF2+ CD3+) cells in these patients. These data suggest that alpha beta TCR-T (gamma delta TCR+ T), CD8, and CD4+ CD8+ cells are important in thyroid destruction in Hashimoto's disease and subacute thyroiditis, and that CD5+ B cells are important in thyroid stimulation in Graves' disease.

Immunology of pregnancy: towards a unifying hypothesis

The variable findings of hormonal-immunoregulation and the variable cellular and humoral immune responses in pregnancy have been considered in relationship to the physiological response. From such considerations it appears that the peripheral blood lymphocyte/leukocyte response in pregnancy is not important, but rather the local uterine immune response at implantation and throughout pregnancy. It is proposed, and evidence is presented, that a normal allogeneic immune response is initiated at the time of implantation of the blastocyst. This immune response regulates the invasive nature of the trophoblast and initiates the first stage of parturition. The initiation and maintenance of this immune response is based on an interplay between maternal and paternal HLA and trophoblast antigens. In the case of HLA-incompatible donor-recipient blastocyst transplants, a more pivotal role for immunoregulation by trophoblast antigens is proposed. This is because it is considered that the local uterine immune response suppresses the expression of allogeneic HLA. This concept is further developed in terms of haploid HLA suppression on maternal and fetal lymphocytes that cross the placenta. This is considered to allow the interaction of these lymphocytes with each other and explains maternal transfer of cell-mediated immunity.

Increase in peripheral natural killer cell activity in patients with autoimmune thyroid disease

Changes in the activity and number of natural killer (NK) cells in peripheral blood in patients with autoimmune thyroid disease were examined. NK activity was measured in a 4-hr 51Cr-release assay and the number of NK cells was analyzed with FITC-conjugated monoclonal antibodies by use of an automated flow cytometer. NK activity in patients with untreated Graves' disease (n = 25, 39.7 +/- 13.5%, P less than 0.05) and Hashimoto's thyroiditis (n = 18, 41.0 +/- 14.2%, P less than 0.05) was high compared to the activity in non-pregnant controls (n = 61, 32.6 +/- 15.0%). NK activity in patients with postpartum Graves' thyrotoxicosis (n = 11, 48.6 +/- 18.9%) was markedly increased compared to the activity in non-pregnant controls (P less than 0.01) and in postpartum controls (n = 29, 33.8 +/- 15.2%, P less than 0.05), although the mean ages of each group did not differ significantly. Moreover, NK activities in the thyrotoxic state were significantly higher than those in the euthyroid state in the same patients with postpartum Graves' thyrotoxicosis or with postpartum destructive thyrotoxicosis. The number of CD16 positive cells increased in patients with postpartum Graves' thyrotoxicosis. However the number of CD16 and CD57 positive cells were normal in all other groups of patients. These results indicate that an increase of NK activity is associated with exacerbation of autoimmune thyroid disease both in Hashimoto's thyroiditis and in Graves' disease and suggest that NK cells might have an important role for the control of disease activity in autoimmune thyroid disease.

Immunoregulatory mechanisms present in the maternal circulation during pregnancy

Systemic alterations of the maternal inflammatory and immune system occur during pregnancy. These changes alone are unlikely to be responsible for the acceptance of the fetal semiallograft. Numerous local events at the maternal-fetal interface appear to be more important. The alterations of the maternal inflammatory and immune systems are subtle enough for no significant increase of infections or malignancy to be apparent. However, 75% of women with rheumatoid arthritis are clinically improved during pregnancy. The effects of pregnancy on polymorphonuclear cells are not likely to be responsible because cell function actually appears enhanced in vivo, despite the fact that pregnancy serum is suppressive in vitro. There is no clear evidence for reduction of monocyte/macrophage function during pregnancy, either in vivo or in vitro. It is unlikely that modulation of B cell phenotype or function is responsible because no suppression is noted, either in vivo or in vitro. Selected products of B cells, immune complexes, appear to be reduced during pregnancy. In patients, the reduction in the concentration of complexes may be due to adsorption by the placenta. The importance of this reduction as a causative factor in the improvement of women with rheumatoid arthritis during pregnancy remains to be determined. Natural killer cell cytotoxicity is decreased during pregnancy. This may in part be due to the release of progesterone induced blocking factor. It is also possible that circulating factors, capable of inhibiting IL-2 release or IL-2 function in vivo, might be responsible. Natural killer cytotoxicity can be normalized by incubation with IL-2. It is unclear how the reduction of natural killer cell activity might systematically affect inflammation or immunity in vivo during pregnancy. In vivo delayed type hypersensitivity appears somewhat reduced during pregnancy. This observation appears consistent with the improvement of rheumatoid synovitis, which is also thought to be T cell mediated. T cell function, measured in vitro, generally appears normal. However, most recent studies have employed mitogens, such as PHA, which is not physiological. Subtle defects involving antigen processing or antigen presentation might be missed in this system. These observations suggest that circulating factors might be important in modulating the cell mediated immune system, in vivo, during pregnancy. While anti-HLA-DR antibodies eluted from the human placenta may be effective therapy in patients with rheumatoid arthritis, their occurrence is too infrequent to account for the improvement seen in afflicted patients.(ABSTRACT TRUNCATED AT 400 WORDS)