title: On the prenatal initiation of T cell development in the opossum Monodelphis domestica.
abstract: Thymus-dependent lymphocytes (T cells) are a critical cell lineage in the adaptive immune system of all jawed vertebrates. In eutherian mammals the initiation of T cell development takes place prenatally and the offspring of many species are born relatively immuno-competent. Marsupials, in contrast, are born in a comparatively altricial state and with a less well developed immune system. As such, marsupials are valuable models for studying the peri- and postnatal initiation of immune system development in mammals. Previous results supported a lack of prenatal T cell development in a variety of marsupial species. In the gray short-tailed opossum, Monodelphis domestica, however, there was evidence that αβT cells were present on postnatal day 1 and likely initiated development prenatally. Demonstrated here is the presence of CD3ε+lymphocytes in late-stage embryos at a site in the upper thoracic cavity, the site of an early developing thymus. CD3ε+cells were evident as early as 48 h prior to parturition. In day 14 embryos, where there is clear organogenesis, CD3ε+cells were only found at the site of the early thymus, consistent with no extra-thymic sites of T cell development in the opossum. These observations are the first evidence of prenatal T cell lineage commitment in any marsupial.
authors.affiliation: Department of Biology, Center for Evolutionary and Theoretical Immunology, University of New Mexico, Albuquerque, NM, USA.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Hansen
authors.affiliation: Department of Biology, Center for Evolutionary and Theoretical Immunology, University of New Mexico, Albuquerque, NM, USA.|National Science Foundation, Arlington, VA, USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Miller
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D005260:Female; D048309:Monodelphis / Q000033:anatomy & histology / Q000196:embryology*; D011247:Pregnancy; D013601:T-Lymphocytes
keywords: T cell; embryonic development; marsupial; thymus