Haematology of foetal sheep

In an attempt to ascertain the means whereby previous exposure to Chlamydophila (C.) abortus can protect against the re-occurrence of enzootic abortion of ewes (EAE), ten previously-exposed ewes were intravenously rechallenged with a large infective dose of C. abortus during pregnancy. The patterns of development of chlamydial placentitis and its sequelae closely resembled that observed following first-time challenge of previously-naïve ewes, although placentitis appeared to develop more slowly following rechallenge infection and none of the rechallenged ewes aborted. Chorioallantoic and foetal pathology and foetal immune responses were qualitatively similar whilst the local maternal response to C. abortus infection of the endometrium did not appear to differ in rechallenged and first-time challenged sheep. This demonstrates that if C. abortus reaches the foetal side of the placenta, a stereotypical response is elicited, regardless of the status of maternal immunity. Therefore it appears that in natural circumstances, acquired immunity of the dam protects against the re-occurrence of EAE by preventing the causative agent from reaching the susceptible foetal trophoblast.

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“…Group C Leucocytic counts were within the expected range for near-term ovine foetuses (Al Salami and Filippich, 1999).…”

Section: Group Bmentioning

confidence: 82%

Rechallenge of previously-infected pregnant ewes with Chlamydophila abortus

et al. 2005

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“…Ovine and human fetuses display similar patterns of lymphoid development in thymus, spleen, lymph nodes, and Peyer's patches, and share similarities in the appearance of circulating leukocytes in blood (15)(16)(17). Because of these developmental similarities, the fetal lamb has frequently been used as a model system to study prenatal development of the mammalian immune system (14,15).…”

Section: Discussionmentioning

confidence: 99%

“…The syndesmochorial placentation of sheep prevents prenatal transfer of maternal Ab, and surgical manipulation of the fetal lamb and pregnant ewe is associated with a low risk of abortion (14). Furthermore, there are many developmental similarities between the ovine and human immune systems (15,16). In particular, mucosal-associated lymphoid tissues develop in the fetuses of both species (17), and it has recently been shown that the gut-associated lymphoid tissue (Peyer's patches) of newborn lambs can respond to enteric vaccination (18).…”

mentioning

confidence: 99%

Oral DNA Vaccination In Utero Induces Mucosal Immunity and Immune Memory in the Neonate

Gerdts

Snider

Brownlie

et al. 2002

The Journal of Immunology

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Infectious diseases are responsible for a significant number of deaths during the first weeks of life. Some of the salient pathogens include HSV, HIV, hepatitis B virus, group B streptococcus, Haemophilus sp., and Chlamydia sp. The vertical transmission of many of these pathogens significantly increases the risk of neonatal infection. We recently reported that oral DNA immunization in utero induced high serum Ab titers and cell-mediated immunity in fetal lambs. In this study, we demonstrate immune memory and mucosal immunity in newborn lambs following oral DNA immunization of the fetus. A single oral exposure in utero to plasmid DNA encoding a truncated form of glycoprotein D of bovine herpesvirus-1 induced detectable immune responses in 80% (12 of 15) of newborn lambs. There was no evidence for the induction of immune tolerance in nonresponding lambs. Responding lambs displayed both systemic and mucosal immune responses and reduced virus shedding following intranasal challenge. Furthermore, strong anamnestic responses were evident for at least 3 mo after birth. The efficacy of in utero oral DNA immunization was further demonstrated with the hepatitis B surface Ag, and protective serum Ab titers occurred in 75% of immunized lambs. Thus, the present investigation confirms that oral DNA immunization in utero can induce both mucosal and systemic immune responses in the neonate and that this immunity has the potential to prevent vertical disease transmission.

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“…The shaping of the early immune system in the sheep is thus determined by factors in the fetus itself. Ovine and human fetuses display similar patterns of lymphoid development in thymus, spleen, lymph nodes and Peyer's patches (PP) and share similarities in the appearance of circulating leucocytes in blood 37–39 . The development of the lymphoid system in fetal lambs occurs over a protracted period of time (gestation period 150 days) 39 .…”

Section: Introductionmentioning

confidence: 99%

Expression of mucosal chemokines TECK/CCL25 and MEC/CCL28 during fetal development of the ovine mucosal immune system

et al. 2007

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Summary CCL25/TECK and CCL28/MEC are CC chemokines primarily expressed in thymic dendritic cells and mucosal epithelial cells. The cognate receptors of CCL25 and CCL28, CCR9 and CCR10, respectively, are mainly expressed on T and B lymphocytes. In human, mouse and pig, CCL25 and CCL28 play a key role in the segregation and the compartmentalization of the mucosal immune system through recruitment of immune cells to specific locations. However, little is known about their role in the ontogeny of the mucosal immune system during fetal development. In the present paper, we report the cloning and the sequencing of ovine CCL25, CCL28, CCR9 and CCR10 and the subsequent assessment of their mRNA expression by q‐polymerase chain reaction in several tissues, including thymus, gut‐associated lymphoid tissue and mammary gland, from young and adult sheep and in the fetal lamb during the development of the immune system. CCL25 mRNA was highly expressed in thymus and gut while CCL28 mRNA was more expressed in large intestine, trachea, tonsils and mammary gland, especially at the end of gestation. These results are consistent with observations in other species suggesting similar roles for these chemokines in sheep. In fetuses, mRNA of CCL25, CCL28 and their receptors are expressed early in the thymus and mucosal tissues, including the small intestine and the nasal mucosa. Furthermore, their expression increased towards the end of gestation. Consequently, we hypothesize that CCL25 and CCL28 play an important role in the lymphocyte colonization of fetal tissues, enabling the development of a functional immune system.

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Haematology of foetal sheep

Cited by 14 publications

References 28 publications

Rechallenge of previously-infected pregnant ewes with Chlamydophila abortus

Rechallenge of previously-infected pregnant ewes with Chlamydophila abortus

Oral DNA Vaccination In Utero Induces Mucosal Immunity and Immune Memory in the Neonate

Expression of mucosal chemokines TECK/CCL25 and MEC/CCL28 during fetal development of the ovine mucosal immune system

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