Enfermedad severa de inclusiones citomegálicas en un feto de una mujer inmunizada antes de la gestación / Severe cytomegalic inclusion disease in the fetus of a woman with preconceptional immunity

El descubrimiento de una microfelalia durante la gestación nos ha incitado a practicar una punción de líquido amniótico para análisis cromosómico y la búsqueda viral por reacción en cadena de la polimerasa (PCR). El análisis realizado ha confirmado una infección fetal por citomegalovirus (CMV) en una madre inmunizada antes de la concepción. El feto presentaba una clásica enfermedad de inclusiones citomegálicas. Se han publicado observaciones similares. Publicaciones recientes explican tales observaciones por la variabilidad de las cepas virales. Estos hechos incitan a estar atentos con los signos ecográficos evocadores de una infección viral en una mujer encinta ya inmunizada: se puede tratar de una reinfección por CMV

Due to detection of fetal microcephaly at 24 weeks' gestation, we performed an amniocentesis at 29 weeks with chromosomal analysis and polymerase chain reaction (PCR) to investigate the presence of viral contamination. Cytomegalovirus (CMV) infection was confirmed by PCR, although the mother had preconceptional CMV immunity. The fetus showed classical CMV inclusion disease. Recent publications explain similar observations by the variability of viral strains. These findings highlight the importance of being alert to ultrasonographic signs of CMV reinfection in pregnant women with preconceptual immunity

Expression of the third complement component (C3) and carboxypeptidase N small subunit (CPN1) during mouse embryonic development.

Complement regulatory proteins prevent excessive complement system activation and deposition, which can lead to host tissue damage, including fetal loss during pregnancy. To further understand the regulation of complement during development, we examined the expression of the complement protein, C3, and the active subunit of carboxypeptidase N (CPN1), the complement anaphylatoxin regulator. RNA and protein analyses indicated that CPN1 expression occurred as early as 8.5 days post coitus (dpc) and continued through birth. At 10.5 and 13.5 dpc, in situ hybridization revealed CPN1 RNA in erythroid progenitor cells. At 16.5 dpc, expression of CPN1 was also detected in hepatocytes. In comparison to CPN1, C3 RNA expression occurred later (after 13.5 dpc). Moreover, C3 expression was limited to the liver erythroid progenitor cells at 16.5 dpc. These results demonstrated that mouse embryos contain RNA and protein for both C3 and CPN1, and CPN1 expression precedes that of C3 by several days.

Markers of fetal growth and serum levels of insulin-like growth factor (IGF) I, -II and IGF binding protein 3 in adults.

Fetal growth has been linked with increased risk of cancer and cardiovascular disease later in life. The insulin-like growth factor (IGF) axis has recently been proposed as a predictor of risk of subsequent cancer and cardiovascular disease. However, only few data are available on the possible association between fetal growth and levels of IGFs later in life. We examined the association between markers of fetal growth, i.e. birth weight, birth length and Ponderal Index, from birth records and serum IGF-I, IGF-II, and IGF binding protein 3 (IGFBP-3) levels in 545 middle-aged Danish men and women. We fitted separate multivariate models including birth weight, birth length, Ponderal Index and serum IGF-I, IGF-II, and IGFBP-3, respectively. After adjustment for age, alcohol intake, smoking, diabetes mellitus, systolic and diastolic blood pressure, serum total cholesterol and current height and weight, we found negative associations between birth weight and Ponderal Index, respectively, and serum IGF-II in men, i.e. the mean regression coefficients were -49.41 (95% CI: -87.06-11.77) (microg/l)/kg and -3.49 (95% CI: -6.73-0.25) (microg/l)/(kg/m3), respectively. Furthermore, in men birth weight was negatively associated with the (IGF-I + IGF-II)/IGFBP-3 and IGF-II/IGFBP-3 ratios, which are believed to be indicators of bioavailable IGF and IGF-II, respectively. However, no other associations were found in any of the models. Between 1 and 16% of the variance in serum IGF-I, IGF-II, and IGFBP-3, respectively, could be explained by the statistical models used in the analyses. We found very little support to the hypothesis of an association between fetal growth and the IGF axis throughout life.

Lymphatic vasculature development.

Although the process of blood vasculature formation has been well documented, little is known about lymphatic vasculature development, despite its importance in normal and pathological conditions. The lack of specific lymphatic markers has hampered progress in this field. However, the recent identification of genes that participate in the formation of the lymphatic vasculature denotes the beginning of a new era in which better diagnoses and therapeutic treatment(s) of lymphatic disorders could become a reachable goal.

Antiphosphatidylserine antibodies affect rat yolk sacs in culture: a mechanism for fetal loss in antiphospholipid syndrome.

PROBLEM: A variety of reproductive impairments have been reported in the context of the antiphospholipid syndrome (APS). APS is associated with the presence of antibodies to negatively charged phospholipids that may affect the outcome of pregnancy. METHOD OF STUDY: Rat embryos were cultured within their yolk sacs. The effects of two antiphosphatidylserine monoclonal aPS antibodies (HL5B, RR7F) regarding their influence on growth and apoptotic events of the yolk sacs, as well as on growth and the morphology of the embryos, were studied. RESULTS: Exposure of rat embryos and their yolk sacs to aPS inhibited yolk sac growth. Moreover, increased number of apoptotic events of giant cells in the aPS-exposed ectoplacental cone was found in comparison with control IgG-exposed giant cells (P < 0.05). No significant damage was observed in the embryos. CONCLUSIONS: The results suggest that aPS affect growth and apoptosis of rat ectoplacental cone.

An essential function for the nuclear receptor RORgamma(t) in the generation of fetal lymphoid tissue inducer cells.

Lymphoid tissue inducer (LTi) cells are associated with early development of lymph nodes and Peyer's patches. We show here that during fetal life the nuclear hormone receptor RORgamma(t) is expressed exclusively in and is required for the generation of LTi cells. RORgamma(t+) LTi cells provide essential factors, among which lymphotoxin-alpha1beta2 is necessary but not sufficient for activation of the mesenchyma in lymph node and Peyer's patch anlagen. This early LTi cell-mediated activation of lymph node and Peyer's patch mesenchyma forms the necessary platform for the subsequent development of mature lymphoid tissues.

Human uterine leukocytes and pregnancy.

In human pregnancy, the embryo implants into the specialized mucosal wall of the uterus (decidua) and the placenta starts to form. Cells from the placenta (trophoblasts) invade into the uterine mucosa in order to open up maternal uterine arteries to ensure an adequate supply of blood to the developing fetus. The trophoblasts have a unique immunological phenotype compared to most cells especially with regard to their expression of major histocompatibility complex (MHC) antigens. On the other side of the interaction, the uterine mucosa (endometrium) differentiates in preparation for implantation. One of the changes that takes place is the appearance in the endometrium of a large number of maternal leukocytes in the final part of the menstrual cycle. If pregnancy ensues, these leukocytes continue to increase in number and are found in close contact with trophoblasts. The composition of this population of maternal immune cells is unusual compared to that seen at other mucosal sites. A lot of research has focused on whether maternal T-cell responses are suppressed or modified during pregnancy. Research has also concentrated on the specialized uterine natural killer (NK) cells, which are found in the decidua in large numbers during early pregnancy. These uterine NK cells have been shown to express receptors for trophoblast MHC antigens, but their role in pregnancy is still mysterious. The purpose of this review is to give an overview of what is known about the immunology at the implantation site and also to provide an update of some of the most recent findings in this field.

Effect of interleukin-10 null mutation on maternal immune response and reproductive outcome in mice.

Interleukin-10 (IL-10) is an anti-inflammatory and immune-deviating cytokine expressed in the endometrium and placenta. IL-10 null mutant (IL-10-/-) mice have been employed to examine the role of IL-10 in regulating immune events in early pregnancy and its significance in implantation and pregnancy success. The inflammatory response elicited in endometrial tissue by insemination was amplified in IL-10-/- mice, with a 66% increase in leukocytes in the endometrial stroma on Day 3 of pregnancy. Despite this, no evidence of abnormal type 1/type 2 skewing was seen in T-lymphocytes from lymph nodes draining the uterus. On Day 18 of gestation, IL-10-/- females mated with IL-10-/- males had 15% more implantation sites and 27% more viable fetuses than pregnant wild-type (IL-10+/+) mice. Placental weight was unaffected, but fetal weight and the fetal:placental weight ratio were higher in IL-10-/- pregnancies. Similar data were obtained in allogeneic pregnancies when IL-10-/- females were mated with major-histocompatibility complex (MHC) disparate IL-10-/- males. Pups delivered by IL-10-/- mothers had increased birth weight and followed an altered growth trajectory, with growth impairment evident from early postnatal life into adulthood, which was reflected in alterations in body composition at 14 wk of age. This study shows that although IL-10 is not essential for maternal immune tolerance or successful pregnancy irrespective of MHC disparity in the fetus, maternal IL-10 is a determinant of growth trajectory in progeny in utero and after birth.

Transcriptional control of murine CD94 gene: differential usage of dual promoters by lymphoid cell types.

The CD94 gene product is involved in controlling NK cell activation, and is one of a family of immune receptors that is found in the NK gene complex in both humans and mice, adjacent to members of the NKG2 family. CD94 forms a heterodimeric complex with several members of the NKG2 family on the surface of NK, T, and NKT cells. These complexes recognize the nonclassical MHC class I molecules HLA-E and Qa-1(b) in humans and mice, respectively. The mechanism for cell type-specific expression of CD94 and other genes from the NK gene complex has not yet been elucidated. In the current study, we show that the murine CD94 gene has two promoters, one of which is upstream of a previously unidentified exon. We illustrate by quantitative real-time PCR that lymphoid cell types use these two promoters differentially and that the promoter usage seen in adult cells is already established during fetal development. We determined that the differential promoter usage by NK cells appears to be susceptible to perturbation, as both the murine NK cell line LNK, as well as cultured C57BL/6 NK cells showed altered promoter usage relative to fresh NK cells. Furthermore, the promoter activity observed in transfection assays did not correlate with expression of the endogenous CD94 gene, suggesting the involvement of chromatin structure/methylation in transcriptional regulation. Our detection of DNase I hypersensitive sites at the CD94 locus that are present only in a cell line expressing endogenous CD94 supports this hypothesis.

Developmental immunology: clinical application to allergy-immunology.

BACKGROUND: An increase in prevalence of allergic diseases has been seen at an unprecedented rate in many countries throughout the world. Associated with this increase in allergic disease has been a disturbing increase in morbidity and mortality of such diseases as asthma despite the availability of several new therapeutic agents over the past 2 to 3 decades. The search for both environmental factors, eg, new allergens, as well as biologic markers of genetic susceptibility, eg, respiratory viruses, has yielded considerable promise for an explanation for this rising prevalence of allergic disease. OBJECTIVE: To present a central unifying hypothesis based upon recent knowledge concerning the developing human immune system and its interaction with external environmental factors, particularly viral infections, as a basis for a clearer understanding of the changing faces of the allergic diseases throughout the lifespan of the individual. DATA SOURCES: English language articles were selected from PubMed, as well as selected abstracts that would have immediate, practical clinical implications. RESULTS: Review of the current literature strongly suggests a relationship between delayed acquisition of Th1 function in the allergy-prone infant, not only as a predictive marker of susceptibility to the development of allergic disease but also as an explanation for the unique vulnerability of these infants to viral infection, eg, bronchiolitis. Furthermore, viral infection during early development in the allergy-prone infant appears to facilitate allergic sensitization in early infancy. This interesting triad of immune deficiency, viral infection, and atopic genetic susceptibility may provide a basis for early detection of allergic disease and may offer new intervention strategies for the prevention of allergic and infectious disease in the young infant.

Maternal immune stimulation reduces both placental morphologic damage and down-regulated placental growth-factor and cell cycle gene expression caused by urethane: are these events related to reduced teratogenesis?

Activation of the maternal immune system in mice decreased cleft palate caused by the chemical teratogen, urethane. Direct and indirect mechanisms for this phenomenon have been suggested, including maternal macrophages that cross the placenta to find and eliminate pre-teratogenic cells, or maternal immune proteins (cytokines) that cross placenta to alleviate or partially alleviate toxicant-mediated effects in the developing fetus. A third mechanism to explain improved fetal developmental outcome in teratogen-challenged pregnant mice might involve beneficial effects of immune stimulation on the placenta. In the present experiments, urethane treatment altered placental morphology and impaired placental function, the latter indicated by down-regulated activity of cell cycle genes and of genes encoding cytokines and growth factors. Maternal immune stimulation with either Freund's complete adjuvant (FCA) or interferon-gamma (IFNgamma) reduced morphologic damage to the placenta caused by urethane and normalized expression of several genes that were down-regulated by urethane. Urethane treatment also shifted placental cytokine gene expression toward a T cell helper 1 (Th1) profile, while immunostimulation tended to restore a Th2 profile that may be more beneficial to pregnancy and fetal development. These data suggest that the beneficial effects of maternal immune stimulation on fetal development in teratogen-exposed mice may, in part, result from improved placental structure and function.

Biological functions of tumor necrosis factor cytokines and their receptors.

Tumor necrosis factor (TNF; formerly known as TNFalpha) and lymphotoxin (LT)alpha, originally characterized by their ability to induce tumor cell apoptosis and cachexia, are now considered as central mediators of a broad range of biological activities. These activities encompass beneficial effects for the host in inflammation and in protective immune responses against a variety of infectious pathogens. TNF family members on the other hand also exert host-damaging effects in sepsis, in tumor cachexia as well as in autoimmune diseases. In addition, the essential roles of the core members of the TNF superfamily, LTalpha, LTbeta, TNF, and LIGHT as well as their receptors during the organogenesis of secondary lymphoid organs and the maintenance of the architecture of lymphatic tissues now becomes appreciated. The elucidation of the biological functions of these cytokines and their specific cell surface receptors has been crucially advanced by the study of gene-targeted mouse strains. This presentation summarizes the roles of TNFR and TNF-like cytokines in infection, sepsis and autoimmunity as well as the pivotal involvement of these molecules in the development of secondary lymphoid organs.

The origin and development of the immune system with a view to stem cell therapy.

Careful study of the phylogeny and ontogeny of the three components of the immune system reveals that the macrophage, lymphatic, and hematopoietic systems originate independently of each other. Chronologically, the most ancient is the macrophage system, which arises in the coelomic cavity as mesenchymal ameboid cells having the properties to recognize self from non-self and to ingest foreign particles. The lymphatic system later develops from the endoderm of pharyngeal pouches, where the thymic anlage differentiates. The lymphocytes that originate here seed all lymphatic organs and retain the ability to divide and thereby form multiple colonies (lymphatic nodules) in the respiratory and digestive tract; further diversification of lymphocytes follows after confrontation with antigens. The last component of the immune system to appear is the hematopoietic system, which originates from the splanchnic mesoderm of the yolk sac as hematogenic tissue, containing hemangioblasts. The hematogenic tissue remains attached to the outer wall of the vitelline vessels, which provides an efficient mechanism for introducing the hematogenic tissue into the embryo. In an appropriate microenvironment, the hemangioblasts give rise to sinusoidal endothelium and to hemocytoblasts - the bone marrow stem cells for erythrocytes, myeloid cells, and megakaryocytes. The facts and opinions presented in this article are not in agreement with the currently accepted dogma that a common "hematolymphatic stem cell" localized in the marrow generates all of the cellular components of blood and the immune system.

Distinct requirements for IL-7 in development of TCR gamma delta cells during fetal and adult life.

TCRgammadelta-transgenic IL-7(-/-) mice were generated to determine whether T cells containing productively rearranged TCRgammadelta genes have additional requirements for IL-7 within the thymus or peripheral lymphoid tissues. Differences in developmental requirements for IL-7 by TCRgammadelta cells were noted and were linked to derivation from fetal- vs adult-type precursors in the thymus. Although TCRgammadelta cells are absent from IL-7(-/-) mice, TCRgammadelta cells were restored to the thymus and periphery by expression of TCRgammadelta transgenes. Endogenous TCRgamma chains were expressed by IL-7(+/-) but not IL-7(-/-) TCRgammadelta-transgenic mice, providing direct support for findings that IL-7 is necessary for rearrangement and expression of TCRgamma genes. The number of TCRgammadelta thymocytes was 10-fold reduced in TCRgammadelta-transgenic IL-7(-/-) embryos; however, adult TCRgammadelta-transgenic IL-7(-/-) or IL-7(+/-) mice had similar numbers of fetal thymus-derived TCRgammadelta cells in their skin. Thus, fetal TCRgammadelta cells required IL-7 for TCR rearrangement, but not for proliferation or survival in the periphery. In contrast, the numbers of TCRgammadelta cells in other tissues of TCRgammadelta-transgenic IL-7(-/-) mice were not completely restored. Moreover, coincident with the transition from the first to second wave of T cell precursors maturing in neonatal thymus, thymus cellularity of TCRgammadelta-transgenic IL-7(-/-) mice dropped significantly. These data indicated that in addition to TCRVgamma gene rearrangement, TCRgammadelta cells differentiating from late fetal liver or adult bone marrow precursors have additional requirements for IL-7. BrdU incorporation studies indicated that although IL-7 was not required for TCRgammadelta cell proliferation, it was required to prolong the life span of mature TCRgammadelta cells.

A role of CXC chemokine ligand 12/stromal cell-derived factor-1/pre-B cell growth stimulating factor and its receptor CXCR4 in fetal and adult T cell development in vivo.

The functions of a chemokine CXC chemokine ligand (CXCL) 12/stromal cell-derived factor-1/pre-B cell growth stimulating factor and its physiologic receptor CXCR4 in T cell development are controversial. In this study, we have genetically further characterized their roles in fetal and adult T cell development using mutant and chimeric mice. In CXCL12(-/-) or CXCR4(-/-) embryos on a C57BL/6 background, accumulation of T cell progenitors in the outer mesenchymal layer of the thymus anlage during initial colonization of the fetal thymus was comparable with that seen in wild-type embryos. However, the expansion of CD3(-)CD4(-)CD8(-) triple-negative T cell precursors at the CD44(-)CD25(+) and CD44(-)CD25(-) stages, and CD4(+)CD8(+) double-positive thymocytes was affected during embryogenesis in these mutants. In radiation chimeras competitively repopulated with CXCR4(-/-) fetal liver cells, the reduction in donor-derived thymocytes compared with wild-type chimeras was much more severe than the reduction in donor-derived myeloid lineage cells in bone marrow. Triple negative CD44(+)CD25(+) T cell precursors exhibited survival response to CXCL12 in the presence of stem cell factor as well as migratory response to CXCL12. Thus, it may be that CXCL12 and CXCR4 are involved in the expansion of T cell precursors in both fetal and adult thymus in vivo. Finally, enforced expression of bcl-2 did not rescue impaired T cell development in CXCR4(-/-) embryos or impaired reconstitution of CXCR4(-/-) thymocytes in competitively repopulated mice, suggesting that defects in T cell development caused by CXCR4 mutation are not caused by reduced expression of bcl-2.

Antibody repertoire development in fetal and neonatal piglets. VI. B cell lymphogenesis occurs at multiple sites with differences in the frequency of in-frame rearrangements.

B cell lymphogenesis in mammals occurs in various tissues during development but it is generally accepted that it operates by the same mechanism in all tissues. We show that in swine, the frequency of in-frame (IF) VDJ rearrangements differs among yolk sac, fetal liver, spleen, early thymus, bone marrow, and late thymus. All VDJ rearrangements recovered and analyzed on the 20th day of gestation (DG20) from the yolk sac were 100% IF. Those recovered at DG30 in the fetal liver were >90% IF, and this predominance of cells with apparently a single IF rearrangement continued in all organs until approximately DG45, which corresponds to the time when lymphopoiesis begins in the bone marrow. Thereafter, the proportion of IF rearrangements drops to approximately 71%, i.e., the value predicted whether VDJ rearrangement is random and both chromosomes were involved. Unlike other tissues, VDJs recovered from thymus after DG50 display a pattern suggesting no selection for IF rearrangements. Regardless of differences in the proportion of IF rearrangements, we observed no significant age- or tissue-dependent changes in CDR3 diversity, N region additions, or other characteristics of fetal VDJs during ontogeny. These findings indicate there are multiple sites of B cell lymphogenesis in fetal piglets and differences in the frequency of productive VDJ rearrangements at various sites. We propose the latter to result from differential selection or a developmentally dependent change in the intrinsic mechanism of VDJ rearrangement.

Functional and morphological development of lymphoid tissues and immune regulatory and effector function in rhesus monkeys: cytokine-secreting cells, immunoglobulin-secreting cells, and CD5(+) B-1 cells appear early in fetal development.

Little is known regarding the timing of immune ontogeny and effector function in fetal humans and nonhuman primates. We studied the organization of lymphocyte and antigen-presenting cell populations in developing lymphoid tissues of rhesus monkey fetuses during the second and third trimesters (65 to 145 days of gestation; term = 165 days). Immunoglobulin-secreting and cytokine-secreting cells were detected at day 80. The thymus, spleen, lymph nodes, and intestinal mucosa were examined for cells expressing CD3, CD5, CD20, CD68, p55, and HLA-DR. In the spleens of 65-day-old fetuses (early second trimester), the overwhelming majority of total lymphocytes were CD5(+) CD20(+) B-1 cells. The remaining lymphocytes were CD3(+) T cells. By day 80, splenic B and T cells were equal in number. Intraepithelial CD3(+) CD5(-) T cells and lamina propria CD20(+) CD5(+) B cells were present in the intestines of 65-day-old fetuses. By day 80, numerous CD20(+) CD5(+) B cells were present in the jejunums and colons and early lymphocyte aggregate formation was evident. The spleens of 80- to 145-day-old fetuses contained immunoglobulin M (IgM)-secreting cells, while IgA-, IgG-, interleukin-6-, and gamma interferon-secreting cells were numerous in the spleens and colons. Thus, by the second trimester, the lymphoid tissues of the rhesus monkey fetus have a complete repertoire of properly organized antigen-presenting cells, T cells, and B cells.

Secretory component, J chain, and immunoglobulins in human embryos and fetuses of the first trimester of pregnancy: immunohistochemical study.

In our previous studies, we described the development of the secretory (mucosal) immune system (SIS) in human fetuses in the second trimester of pregnancy. In the present study, we examined the presence and distribution of components of this system in human embryos and early fetuses in the first trimester. An immunohistochemical study was performed on 17 embryos and 9 fetuses (4 to 12 wk of development) using antibodies against secretory component (SC), joining (J) chain, immunoglobulins (IgA, IgM, IgG), subsets of T and B lymphocytes, and macrophages. Cells positive for SC, J chain, and IgG were found in epithelial tissues from wk 4 of pregnancy. In the internal organs, such as the myocardium and endocardium, capillary endothelium, epithelium of the kidney tubules and some others, only J chain and immunoglobulins were seen. IgA was weakly reactive in tissues where SC and/or J chain were presented. IgM was very weak or absent. Among the cellular components of the SIS, only macrophages were seen in 4-wk-old embryos. CD3+ and CD20+ lymphocytes were found at wk 7 to 8. IgA- and IgM-positive lymphocytes appeared at the end of wk 9. The SIS is widespread in embryonic and early fetal periods and begins to function before the appearance of the common immune system in the developing organism. The first functional components of the SIS, such as IgG and IgA observed in this study, are most probably of maternal origin.

Antibodies to folate receptors impair embryogenesis and fetal development in the rat.

BACKGROUND: Folic acid (FA) supplementation reduces neural tube defects (NTDs) by 70%. However, the cause of most NTDs cannot be attributed to folate deficiency, to mutations of genes that encode folate pathway enzymes, and folate receptors (FRs) that mediate cellular folate uptake. Mouse embryos nullizygous for the ortholog of the FRalpha gene have lethal congenital abnormalities that are preventable by administration of folinic acid to the dams. To determine whether antibodies to FRs are similarly teratogenic, we studied a rat model. METHODS: Immunohistochemistry with an antiserum to rat FRs was used to identify the receptors on reproductive tissues and embryos. Gestation day (GD) 8 rats received intraperitoneal injections of antiserum to the FRs, and their embryos were examined 2-9 days later. Some rats received pharmacologic doses of folinic acid or dexamethasone before the antiserum was administered. RESULTS: The FRs are present on oocytes, the oviduct, and uterine epithelial cells, and in the embryo at all stages examined between GD4 and GD15. The antiserum has a dose-related effect on embryo viability and organogenesis. Folinic acid prevented teratogenicity resulting from smaller doses of antiserum, but not that caused by larger doses. Resorption of embryos with the larger doses of the antiserum was prevented by dexamethasone. CONCLUSIONS: FRs are expressed on oocytes, epithelial cells of reproductive organs, and embryonic and extraembryonic tissues. Antiserum to FRs administered to pregnant rats causes embryonic damage. Embryo lethality with smaller doses of antiserum is preventable by administration of folinic acid, while larger doses cause embryo damage by immune-mediated cell lysis, which can be prevented by dexamethasone.

The rat as a model in developmental immunotoxicology.

Evidence is presented to demonstrate that the rat is a sensitive rodent species for developmental immunotoxicity testing of chemicals. A battery of immune function assays was performed in adult rats, which were exposed perinatally (i.e., during gestational, lactational, and/or juvenile development) to three different classes of environmental chemicals. The chemicals employed were the following: the organotins di-n-octyltindichloride (DOTC) and tributyltin oxide (TBTO); the polyhalogenated aromatic hydrocarbon 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD); and the organochlorine pesticides methoxychlor (MXC) and heptachlor (HEP). Suppression of immune function was observed in adult rats exposed to each of these chemicals during immune system development. The duration of immune function suppression in the rats so exposed ranged from three weeks (i.e., DOTC and MXC) to 19 months (i.e., TCDD) after the last exposure to the chemical.