Immature, double negative (CD4-,CD8-) rat thymocytes do not express IL-2 receptors.
IL-2R alpha-chain is expressed on a subset of mouse CD4- and CD8-, double negative (DN) thymocytes. This expression of IL-2R alpha-chain on some DN thymocytes in the mouse has led to the proposal that IL-2 might serve as a principal growth and/or differentiation factor for immature thymocytes. However, previous histologic observations have indicated that IL-2R alpha-chain is not expressed on the subcapsular thymic blasts (an area rich in DN cells) in either huma or rat thymus, whereas all three species display IL-2R expression on a few cells in the thymic medulla. Therefore, we characterized rat DN thymocytes to determine whether they contained an IL-2R+ population. The results show that rat thymic DN cells share several characteristics with mouse DN cells. However, most of the rat strains do not express the IL-2R on DN cells as shown either by immunofluorescence or by IL-2 binding and receptor cross-linking. Thus, the rare medullary IL-2R+ cells were not found in the DN cells. Only in the exceptional F344 rat strain is the IL-2R alpha-chain expressed on a major proportion of thymocytes, including both DN cells and small cortical-type thymocytes. Furthermore, rat DN cells do not contain detectable IL-2 mRNA or cytoplasmic IL-2 activity, thus supporting the conclusion that it is unlikely that IL-2 and IL-2R serve to maintain the proliferation of rat DN thymocytes in vivo. The possible significance of in vivo expression of IL-2R alpha-chain on immature thymocytes in the mouse and in a single rat strain is discussed.
Takács
L
L
Laboratory of Molecular Immunoregulation, National Cancer Institute, Frederick, MD 21701-1013.
Ruscetti
F W
FW
Kovacs
E J
EJ
Rocha
B
B
Brocke
S
S
Diamantstein
T
T
Mathieson
B J
BJ
D000375:Aging; D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte; D002454:Cell Differentiation; D002469:Cell Separation; D003208:Concanavalin A; D004622:Embryo, Mammalian; D007150:Immunohistochemistry; D008213:Lymphocyte Activation; D051381:Rats; D011915:Rats, Inbred BUF; D011916:Rats, Inbred F344; D011917:Rats, Inbred Lew; D011920:Rats, Inbred WF; D015375:Receptors, Interleukin-2 / Q000378:metabolism*; D013601:T-Lymphocytes / Q000145:classification* / Q000166:cytology / Q000378:metabolism; D013950:Thymus Gland / Q000254:growth & development* / Q000276:immunology / Q000378:metabolism
D000945:Antigens, Differentiation, T-Lymphocyte; D015375:Receptors, Interleukin-2; D003208:Concanavalin A