© 1975 by The Society for Integrative and Comparative Biology
Ontogenic Studies of Antigen Binding Cells in the Dual Thymus Glands of the South American Rodent, Octodon degus
Department of Medical Microbiology, College of Medicine, University of Vermont Burlington, Vermont 05401
Octodon degus (the degu) has two anatomically separate thymus glands, a cervical thymus (CT) and a mediastinal thymus (MT). Antigen binding cells taken from the two thymic components of fetal and neonatal degus were enumerated by incubation with beta-galactosidase (Gz) as antigen, followed by incubation with 5-bromo-4-chloro-3-indolylbeta- D- galactoside (BIG). Gz cleavage of BIG on the surfaces of Gz antigen binding cells (ABC's) produces an indoxan catalytic product which stains the cell blue. Histochemically tained cells are interpreted as antigen binding cells with antigen receptors specific for Gz. The frequencies of ABC's in neonatal CT and MT were approximately 0.1% and 0.01%. Cortisone treatment increased the frequency of Gz ABC's, whereas Gz immunization resulted in a rapid elimination of Gz ABC's. Cortisone treatment delayed the loss of Gz ABC's in neonatal degus treated with both cortisone and Gz. Both fetal and neonatal degus may have no detectable Gz ABC's in either CT, or MT, or both. The data are interpreted with respect to current hypotheses for maturation of immunological repertoire, and pluripotentiality versus unipotentiality of antigen sensitive cells. The cervical and mediastinal thymic components of the degu may serve as independent sites for the development of immunocompetent thymocytes.