title: Histogenesis of B and T lymphocytes.
abstract: There are striking differences in the histogenesis of B and T cells. 1) The formation of B lymphocytes seems to be closely associated with that of other blood cells, whereas the formation of T cells is not. 2) In postnatal life, the bone marrow is a mojor site for the formation of B cells, while T cells are produced mainly in the thymus. 3) B cells are formed in a short production pathway, consisting of two or three mitoses, whereas T cells are formed in a long production pathway, consisting of about eight mitoses. 4) The starting point for the short production pathway is a large transitional cell. The long production pathway starts with a reticulum cell, a large lymphoblast or a cell which has been termed "monocytoid". 5) Plasma proteins have ready access to the cells of the short production pathway in bone marrow, but because of the blood-thymus barrier are not as readily accessible to the tissure involved in T cell formation in the long production pathway in the thymus.
mesh_terms: D000367:Age Factors; D000918:Antibody Specificity; D000941:Antigens; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D001666:Binding Sites, Antibody; D001854:Bone Marrow Cells; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000166:cytology; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D008198:Lymph Nodes / Q000166:cytology; D011947:Receptors, Antigen, B-Cell / Q000032:analysis; D013601:T-Lymphocytes / Q000166:cytology*
chemical_list: D000941:Antigens; D007074:Immunoglobulin G; D011947:Receptors, Antigen, B-Cell