title: Analysis of lymphocyte phenotypes in cord blood from early gestation fetuses.
abstract: Using cord blood samples obtained from fetuses between 16 and 40 weeks gestation, we have used a lysed whole blood flow cytometric technique to study the natural history of lymphocyte phenotypes known to be highly represented in cord blood at birth. The majority (51.0 +/- 14.7%) of lymphocytes expressed CD45RA, a marker of 'virgin' cells and there was a correlation between increasing percentages of CD45RA+lymphocytes and gestational age (r = 0.44, P < 0.01). Few cells (8.5 +/- 4.2%) expressed the CD45RO marker of primed lymphocytes and very few (1.0 +/- 0.7%) co-expressed CD45RA and RO, indicating little traffic between the two maturation markers. The percentage of B lymphocytes co-expressing CD5 was high in the fetal circulation (55.5 +/- 10.5%) compared with healthy adults (23.2 +/- 14.3%; P < 0.00001) and the level of CD5+ B cells declined with gestational age in an exponential manner (r = -0.45, P < 0.05). Similarly, levels of T lymphocytes expressing the gamma delta T cell receptor (TCR) declined exponentially (r = -0.59, P < 0.005). These results demonstrate that lymphocytes remain almost entirely unprimed before birth. In addition, CD5+ B lymphocytes and TCR-gamma delta+ T lymphocytes decline exponentially towards birth, in a manner suggesting that they may be seeding peripheral sites such as the spleen, skin and mucosae.
authors.affiliation: Department of Immunology, King's College School of Medicine and Dentistry, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Peakman
authors.forename: A G
authors.initials: AG
authors.lastname: Buggins
authors.forename: K H
authors.initials: KH
authors.lastname: Nicolaides
authors.forename: D M
authors.initials: DM
authors.lastname: Layton
authors.forename: D
authors.initials: D
authors.lastname: Vergani
mesh_terms: D015703:Antigens, CD / Q000378:metabolism*; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism; D018956:CD5 Antigens; D005312:Fetal Blood / Q000166:cytology*; D005865:Gestational Age; D006801:Humans; D017493:Leukocyte Common Antigens / Q000378:metabolism; D016131:Lymphocyte Subsets / Q000166:cytology*; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000378:metabolism; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte; D018956:CD5 Antigens; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta; D017493:Leukocyte Common Antigens