Receptors for T cell-replacing factor/interleukin 5. Specificity, quantitation, and its implication.
T cell-replacing factor (TRF)/IL-5 is a glycosylated polypeptide that acts as a key factor for B cell growth and differentiation. Since IL-5 action is probably mediated by specific cell surface receptor(s), we have characterized the binding of IL-5 to cells using biosynthetically [35S]methionine-labeled IL-5 and 125I-IL-5 that had been prepared using Bolton-Hunter reagent. The radiolabeled IL-5 binds specifically to BCL1-B20 (in vitro line) (a murine chronic B cell leukemic cell line previously shown to differentiate into IgM-secreting cells in response to IL-5) within 10 min at 37 degrees C. There are two classes of binding sites with high affinity (Kd = 66 pM) and low affinity (Kd = 12 nM) for IL-5 and an average number of binding sites for high affinity and for low affinity were 400 and 7,500 per cell, respectively. The specificity of binding of radiolabeled IL-5 has been confirmed by demonstrating that only unlabeled IL-5 and anti-IL-5 mAb but not by IL-1, IL-2, IL-3, IFN-gamma, and GM-CSF inhibit radiolabeled IL-5 binding to BCL1-B20 cells. Treatment of surface-bound radiolabeled IL-5 with bivalent crosslinkers identified a membrane polypeptide of Mr 46,500 to which IL-5 is crosslinked. A variety of cell types have been surveyed for the capacity to bind specifically radiolabeled IL-5 with high affinity. BCL1 cells MOPC104E (murine myeloma cell line) expressed IL-5-R, whereas BAL. 17 and L10 A (B cell lymphoma) did not. T cell line, mastocytoma cell line, or macrophage tumor cell line did not display detectable levels of IL-5-R. were hardly detectable on normal resting B cells but were expressed on LPS-activated B cells, fitting the function of IL-5 that acts on activated B cells for their differentiation into Ig-secreting cells. Intriguingly, early B cell lines (J-87 and T-88) that grow in the presence of IL-5 expressed significant but low numbers of high-affinity binding sites for IL-5. The biological effects of IL-5 were mediated by high-affinity binding sites. The identification and characterization of IL-5-R should provide new insight into the apparent diverse biological activities of IL-5.
Mita
S
S
Department of Biology, Kumamoto University Medical School, Japan.
Harada
N
N
Naomi
S
S
Hitoshi
Y
Y
Sakamoto
K
K
Akagi
M
M
Tominaga
A
A
Takatsu
K
K
D000345:Affinity Labels; D000818:Animals; D001667:Binding, Competitive; D001681:Biological Assay; D002462:Cell Membrane / Q000378:metabolism; D015848:Interleukin-5; D007378:Interleukins / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D011971:Receptors, Immunologic / Q000378:metabolism*; D018123:Receptors, Interleukin; D053649:Receptors, Interleukin-5; D014407:Tumor Cells, Cultured
D000345:Affinity Labels; D015848:Interleukin-5; D007378:Interleukins; D011971:Receptors, Immunologic; D018123:Receptors, Interleukin; D053649:Receptors, Interleukin-5