title: Lymphoid-epithelial secretory immune system in human fetuses in the second trimester of gestation.
abstract: The development of the secretory immune system (SIS) in the respiratory, digestive, and urogenital tracts and other organs of fetuses in the second trimester of gestation is described. Tissues of all internal organs of human fetuses (n = 36) that had died between 13 and 25 weeks of gestation were studied immunohistochemically for the presence of secretory component (SC), J chain, IgA, IgM, IgG, macrophages, and different subsets of lymphocytes. We found protein elements of the SIS in fetuses during the entire second trimester in the epithelium of the digestive, respiratory, and urinary tracts; in hepatocytes; in the epithelium of the bile duct, renal tubules, and all the urinary tract; in the salivary glands, pancreas, and thyroid; in the epithelium of the Fallopian tubes and uterus; in the epididymis and the rete testes; in the skin; and in other organs. Immunocompetent cells, including IgA- and IgM-secreting cells, were located in these organs under the epithelium and sometimes between epithelial cells. In fetuses with acute infection, the number of immunocompetent cells was higher, reflecting a whole-immune system reaction, including the SIS. We conclude that the fetal SIS is a ramified, defensive immune system that is distributed throughout most organs of epithelial origin in second-trimester fetuses, and that it reacts against intrafetal infiltration by foreign antigens.
authors.affiliation: Department of Obstetrics and Gynecology, Kaplan Medical Center, Rehovot 76100, Israel.
authors.forename: Pavel
authors.initials: P
authors.lastname: Gurevich
authors.forename: Herzl
authors.initials: H
authors.lastname: Ben-Hur
authors.forename: Sergio
authors.initials: S
authors.lastname: Szvalb
authors.forename: Moisey
authors.initials: M
authors.lastname: Moldavsky
authors.forename: Itshak
authors.initials: I
authors.lastname: Zusman
mesh_terms: D000328:Adult; D005314:Embryonic and Fetal Development; D005260:Female; D005333:Fetus / Q000276:immunology*; D006801:Humans; D007107:Immune System / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D007144:Immunoglobulin J-Chains / Q000032:analysis / Q000096:biosynthesis; D008214:Lymphocytes / Q000166:cytology / Q000378:metabolism; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012635:Secretory Component / Q000032:analysis / Q000096:biosynthesis*
chemical_list: D007144:Immunoglobulin J-Chains; D012635:Secretory Component