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Autonomy of the PHA‐Responsive Cells in the Mouse Thymus
Author(s) -
Jacobsson Hans,
Blomgren Henric
Publication year - 1974
Publication title -
scandinavian journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.904
H-Index - 84
eISSN - 1600-0609
pISSN - 0036-553X
DOI - 10.1111/j.1600-0609.1974.tb00191.x
Subject(s) - thymectomy , biology , phytohaemagglutinin , population , lymphopoiesis , thymocyte , spleen , transplantation , cell , immunology , renal capsule , repopulation , andrology , lymphocyte , haematopoiesis , bone marrow , microbiology and biotechnology , t cell , endocrinology , medicine , kidney , immune system , stem cell , genetics , myasthenia gravis , environmental health
Lymphopoiesis in the thymus and the size attained by the gland, unlike peripheral lymphoid organs, is considered not to be influenced by any external homeostatic forces. Recently it was observed that a minority of the thymic cells, approximately 5 %, are immunocompetent and respond to phytohaemagglutinin (PHA) by an increased DNA synthesis. In the present investigation we have tested whether the size of this subpopulation of cells is also maintained in an autonomous way. Thymectomized and sham thymectomized adult mice were lethally X‐irradiated and reconstituted with syngeneic bone marrow or foetal liver cells. Such animals received a thymus graft, obtained from newborn syngeneic donors, under the kidney capsule. At various times after transplantation the cell numbers in the grafts were established and their in vitro responsiveness to PHA determined. It was observed that neither the total cell number nor the size of the PHA‐responsive cell population differed whether the host's thymus was removed or not. In other experiments thymic repopulation was studied in lethally irradiated mice reconstituted by haemopoietic cells only or together with PHA‐responsive thymocytes injected i.v. These experiments showed that re‐population of the total thymic cell population as well as its subpopulation of PHA‐responsive cells was not influenced by the presence of PHA‐responsive, thymus‐derived cells in peripheral organs. These experiments support the view that not only the size of the cortical thymocyte population, constituting the majority of the thymic cell population, but also that of the medullary one which contains the PHA‐responsive celle is maintained in an autonomous way not influenced by specific external feed‐back mechanisms.