Identification of a soluble IL-2 receptor beta-chain from human lymphoid cell line cells.
A clone was isolated from the human lymphoid cell line YT that displayed IL-2R beta, and was found to express much higher levels of IL-2R beta than the original cells. Combining cell surface iodination, affinity labeling of the released soluble protein, and fluorescence sandwich-ELISA for both IL-2 and IL-2.(soluble)(s)IL-2R beta reactants revealed the presence of IL-2-binding protein in the culture supernatant as soluble forms of IL-2R beta. By using the fluorescence sandwich-ELISA elevated levels of sIL-2R beta were measured in culture supernatants of human T cell leukemia virus I positive T cell lines. In addition to this constitutive production of sIL-2R beta, normal PBMC could release low levels of IL-2R beta by stimulation with PHA. In contrast, this was not found in certain human T cell leukemia virus I negative T cell, B cell and macrophage lines. Immunoprecipitation of the soluble protein with IL-2R beta-specific mAb characterized it as an apparent 50- to 55-kDa molecule that is distinct from the 45-kDa soluble IL-2R alpha. Moreover, 10 to 15% of the total cell surface molecules were released into culture supernatants. These results suggest that the released IL-2R beta might serve as an immunoregulatory function in IL-2 dependent both normal and abnormal immune responses.
Honda
M
M
AIDS Research Center, National Institute of Health, Tokyo, Japan.
Kitamura
K
K
Takeshita
T
T
Sugamura
K
K
Tokunaga
T
T
D006801:Humans; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism*; D008970:Molecular Weight; D011233:Precipitin Tests; D015375:Receptors, Interleukin-2 / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D012995:Solubility; D014407:Tumor Cells, Cultured / Q000737:chemistry
D007376:Interleukin-2; D015375:Receptors, Interleukin-2