Immunological mechanisms in human reproduction - itslearning

Immunologicalmechanisms in humanreproductionMOL8002Molecular mechanisms of host defenceNovember 2009Guro Dalheim OlsenHuman reproduction research group, IKM, NTNUhttp://www.ntnu.no/dmf/ikm/cellebiologi/reproduksjon

Agenda• Pregnancy• Trophoblasts• The placenta• Inflammation – pre-eclampsiaeclampsia, metabolicsyndrome and cardiovascular diseases• Toll-likelike receptors• The HUNT study• Suggested reading

Postulations of pregnancy• Pregnancy is a condition of immunologic armistice.• The maternal-fetalinteraction is a major challenge forthe immune system, and a state of immune tolerancehas to be established between the coexisting motherand fetus.• Some postulations of pregnancy:1. Natural immune suppression: : a general immune suppressionstate is generated during pregnancy to favour immuneacceptance between the mother and fetus.2. Fetal cells (the(trophoblasts) have to interact with maternalimmune cells: expression of HLA.3. Placenta is an immune privileged site: mechanisms fordestroying activated immune cells.

Trophoblasts• Embryonic stem cells with outstanding capasity of adapting tochanging environments, tissue remodelling and organdevelopment.• Cells forming the outer layer of a blastocystcyst. Provide nutrients tothe embryo and develop into a large part of the placenta.• Formed during the first stage of pregnancy and are the first cellsto differentiate from the fertilized egg.• Cytotrophoblasts: : forms the inner layers• Syncytiotrophoblasts: : forms the outer layers• Villous syncytiotrophoblasts: grow in a few areas and createanchoring coloumns into maternal tissues• Extravillous trophoblasts: invade the decidua

Moffet-King A, Nature Rev Immunol 2002; 2 (9): 656.• CT: Cytotrophoblast• T: Trophoblast• F: Fibrinoid material• E: Endovascular trophoblast• GC: Placental-bed giant cells• K: NK cells• M: Macrophages• L: T cells

The placenta• Constitutes a physical and immunological barrier,protecting the fetus against invading infectious agentsand inflammation.• A pregnancy-specific component of the innateimmune system.• Supplies the fetus with oxygen and nutrients, andallows fetal waste to be disposed via the maternalkidneys.• Develops from the same sperm and egg cells that formthe fetus, and functions as a fetomaternal organ withtwo components, the fetal part (Chorion(frondosum),and the maternal part (Decidua(basalis).

Photo: Irina P. Eide

Photo: Irina P. Eide

Inflammationhttp://www.chronicprostatitis.com/images/f3.jpg

The inflammatory response andpregnancy• Normal pregnancy is characterized by a mild systemicinflammatory response. . The mild inflammatory changes do notindicate illness.• Resembles the acute phase response: activated endothelium,increased plasma fibrinogen, PAI-1,caeruloplasmin, redusedplasma albumin, increase of CRP.• During first trimester: leukocytosis, activated neutrophils andincreased phagocytosis.• Strengthened systemic inflammatory response as pregnancyadvances, peaking during the third trimester (increase(of IL-6,TNF-a, circulating markers of oxidative stress, some timesinsulin resistance).• A more vigorous systemic inflammatory response than normalpregnancy: pre-eclampsiaeclampsia.

The amount of microparticlesincreases during pregnancy1. trim 2. trim 3. trimDuring normal pregnancy:Small amounts ofmicroparticles that are takencare of by the maternalimmune system.Syncytiotrophoblast microparticles (SMBM)bind to maternal monocytes, myeloiddendrittic cells, and stimulate PBL toproduce proinflammatory cytokines. STBMalso have a direct effect on endothelial cells -downregulate proliferation and activation.Upregulation of cytokines.MORE OF ALL THIS CAN RESULT INPRE-ECLAMPSIA!

Pre-eclampsiaeclampsia (PE)• Pregnancy-associatedassociated complication• Characterized by hypertention, proteinuria and activation ofmaternal endothelium• Risk of PE is 2.5% in unselected Norwegian pregnancies• Abnormal interaction between maternal and fetal tissues duringplacentation• Trophoblast invasion in the uterine spiralarteries is limited →hypoxia and release of factors to maternal circulation →maternal vascular endothelial cell dysfunction• Increased level of ROS, proinflammatory cytokines, subsequentendothelial activation and inflammationMAY BE AN ABNORMAL PREGNANCY IN A NORMAL WOMANORMAY BE A NORMAL PREGNANCY IN AN ABNORMAL WOMAN

Suggested two-stagemodel for PEREDUCEDPLACENTALPERFUSION(stage 1)MATERNALCONSTITUTIONALFACTORS (genetic,environmental, obestity,diabetes, diet)OXIDATIVE STRESSACTIVATEDMATERNALENDOTHELIUMPRE-ECLAMPSIA(stage 2)Modified from Roberts J et al. Lancet 1999;354:788.

Trophoblast invasion of the deciduaDeciduaMyometriumMoffet-King A, Nature Rev Immunol 2002; 2 (9): 656.

Failing the ”pregnancy test”Event thresholdNormal pregnancyPathology giving eventsMETABOLIC DEMANDS EXCEED BUFFERING CAPACITIES

Metabolic syndrome• Hallmarks: obesity,disturbance ofglucose metabolism,dyslipidemia andhypertension• Risk factors forcardiovasculardiseases• Runs in families –genetic basis?• Severe increaseduring the recentyears (age, women)http://archimede.bibl.ulaval.ca/archimede/files/4ae1756d-dc83-4b9d-8c80-a5df2dfe51f0/22151004.jpg

INFLAMMATORY RESPONSEENDOTHELIAL DYSFUNCTIONMETABOLICSYNDROMEINSULIN RESISTANCEPRE-ECLAMPSIADYSLIPIDAEMIAHDL, TGCOAGULATIONDISTURBANCES

Pregnancy represents a considerablemetabolic and vascular ”stress” testWomen with pregnancies complicated by IUGR, pre-eclampsia and/or premature deliveries have increasedrisk for cardiovascular diseasesLOW BIRTHWIGHT 4.3PREMATURE DELIVERY 5.2PRE-ECLAMPSIA ECLAMPSIA 17.2

Pre-eclampsiaeclampsia vscardiovascular disease• Both are inflammatory disorders:Endothelial dysfunction andactivation, increased levels ofoxidative stress markers andproinflammatory cytokines• PE is associated with an increased riskof later life CVD• Inflammatory cytokine/cytokineRgene polymorphisms → increased PErisk• Increased frequency of other genevariants involved in inflammation inHUNT2 PE cases (SEPS1,(ACVR2)• CVD: polymorphisms of genesinvolved in specific biochemicalpathways related todevelopment/progression ofatherosclerosis

Toll-likelike receptors (TLRs)http://www.mcb.uiuc.edu/faculty_research/images/tapping.jpg

Toll-likelike receptors (TLRs)• Activation of TLRs initiates a series of signaling events that triggerinnate immune responses through NF-κB-dependent and IRF-dependent signaling pathways, inducing expression ofproinflammatory genes (cytokines, IFNs and chemokines).• TLRs are PRRs that collectively recognize PAMPs (lipids,carbohydrate, peptide and nucleic-acidstructures) ) and DAMPs(celldamage and cellular stress-signals;signals; Hsp, , fibrinogen, heparansulfat, HMGB1). DAMPs possess inflammatory properties, , andsignal mainly through TLR2, TLR4 and RAGE.• HMGB1 is released from necrotic cells, inducing inflammation andthe recruitment of mononuclear cells to the site of tissue damage.• The human placenta also releases HMGB1 and thus has thepotential to mount inflammation. Elevated decidual HMGB1expression has been suggested a role in development of PE.• HMGB1-mediatedinflammatory response has also been implicatedin the pathogenesis of CVD.

TLRs in pregnancyKoga, K. & Mor, G. Repr. Sci. 2008; 15 (3): 231-242.

TLR polymorphisms (SNPs)• Inflammatory diseases- asthma, allergy and atopic eczema in children- type 1 diabetes- Chron’s disease• Pregnancy complications- premature birth, low birth weight- maternal anemia- chorionic plate inflammation- increased susceptibility to infections in pregnancy• Cardiovascular diseases- acute coronary events- reduced carotid artery intima-mediamedia thickness, decreased risk of atherogenesis- atherosclerosis

To summarize…• TLR2, TLR4 and TLR9 play a role in inflammation – and thus,probably in diseases caused by abnormal inflammatory reactions.• It seems likely that knowledge gained about genes of influence inPE pathogenesis also will provide insight into genetic factorsrelevant to CVD – and vice versa.• Since CVD manifestations and gene regulation are influenced bygender, the ”PE-approach” may provide useful informationabout gender specific phenomena in CVD.

HUNTThe Nord-TrTrøndelagHealth Study• HUNT 1, 2 & 3• 130 000 inhabitants in Nord-Trøndelagcounty ~ 70% participated• Stable/homogenous population• Peripheral blood wasretrieved and storedin HUNT Biobank• Case/control study(geneticsand pre-eclampsia)• SNP genotyping(SNPlex, Illumina)• GWAS (Illumina(Illumina)HUNT Biobank, Levanger

Thanks for your attention!☺Suggested reading:1. Borzychowski AM et al. Inflammation and pre-eclampsiaeclampsia. Fetal andNeonatal Medicine 2006; 11: 309.2. Koga K et al. Toll-likelike receptors and pregnancy: : Trophoblasts asmodulators of the immune response. J Obstet Gynaecol Res 2009;35 (2):191.3. Patni S et al. An introduction to Toll-likelike receptors and their possiblerole in the initiation of labour. BJOG 2007; 114: 1326.4. Sibai B et al. Pre-eclampsiaeclampsia. Lancet 2005; 365: 785.