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A fetus needs to defend itself against foreign bodies—so how does it

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first_img By Gretchen VogelJun. 14, 2017 , 1:00 PM The developing immune system has a built-in control mechanism that prevents it from attacking the mother’s cells. A fetus needs to defend itself against foreign bodies—so how does it avoid attacking its mother? The immune system of a fetus developing in the womb faces a quandary: It has to prepare itself to attack dangerous pathogens after birth, by distinguishing its own cells from those of invaders. But until that time, it needs to avoid attacking the mother, whose cells are also “foreign.” A new study of fetal tissue has revealed one way the developing immune system keeps itself in check: by interrupting the production of a key weapon in the body’s arsenal against invaders.The new insights might help researchers better understand certain types of miscarriages and a deadly immune response in premature babies. It also could lead to new ways to keep the adult immune system in check when it gets out of balance.To better understand how the different pieces of the immune system develop, immunologists Florent Ginhoux and Naomi McGovern at the Agency for Science, Technology and Research (A*STAR) in Singapore and their colleagues studied tissue from nearly 100 elective abortions performed between 14 and 22 weeks of gestation. Consistent with other studies, they found that as early as 13 weeks of development, the fetus was producing a range of immune system cells, including dendritic cells, which recognize invaders and signal other immune cells to attack. These cells were fully functional, the researchers found: In lab experiments, they responded as well as adult dendritic cells to molecules that mimic pathogens, the researchers report today in Nature. Email Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwecenter_img Dendritic cells usually send out signals that ramp up proliferation of another type of immune cell, T cells, which then attack invaders. But when the researchers added the dendritic cells to a mix of adult immune cells, the fetal dendritic cells triggered more than the usual number of T regulatory cells, which keep the production of T cells in check. The researchers also found that different genes were switched on in fetal dendritic cells than in adult dendritic cells. In particular, fetal cells made high amounts of arginase-2, an enzyme that breaks down L-arginine, a key ingredient in the production of a key messenger named tumor necrosis factor alpha (TNF-alpha). TNF-alpha triggers inflammation, a general state of war against an invader; make less of it, and your immune system reacts less aggressively. “The system is fully active and able to respond,” Ginhoux says, but at the same time it has built-in brakes.The insight “builds nicely on a number of studies” showing that parts of the fetal immune system are in place fairly early in development, says Jakob Michaelsson, an immunologist at the Karolinska Institute in Stockholm. The fetal cells’ ability to keep the immune response in check is quite potent, he says, and harnessing that ability in adults could lead to new ways to treat autoimmune diseases, in which the body improperly attacks its own cells. In another set of experiments, the researchers found that fetal dendritic cells could block the production of TNF-alpha by adult T cells as well.Ginhoux and his colleagues also note that high levels of TNF-alpha are common in some types of miscarriage, gestational diabetes, and necrotizing enterocolitis, an out-of-control immune reaction that often afflicts premature infants. The arginase-2 pathway might be a way to better understand and perhaps find treatments for those conditions, Ginhoux says. Sign up for our daily newsletter Get more great content like this delivered right to you! Country angelhell/iStockphoto Click to view the privacy policy. Required fields are indicated by an asterisk (*)last_img

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