Low affinity IgE receptors: regulation and functional roles in cell activation.
The low affinity IgE receptors (Fc epsilon RII/CD23) homologous to animal lectins have the unique property of cleaving-off the extracytoplasmic portion as the soluble form (IgE binding factor; IgE-BF). Molecular analysis using Fc epsilon RII/CD23 cDNA proved that Fc epsilon RII is not unique to B lymphocytes but is expressed on a variety of cell lineages including T lymphocytes, macrophages and eosinophils. In these cell types, IL-4 is a general inducer of this molecule while IFN-gamma down-regulates B cell Fc epsilon RII/CD23 and up-regulates Fc epsilon RII/CD23 on macrophage and eosinophil cell lines. As predicted by the expression of Fc epsilon RII/CD23 in some HTLV-1(+) T cell lines, Fc epsilon RII/CD23 proved to be induced on normal peripheral T lymphocytes by IL-4 or IL-2 in the presence of additional permissive signals. As indicated by IL-2-dependent Fc epsilon RII/CD23 induction, there is an interesting bilateral co-regulation between Fc epsilon RII/CD23 and the 55 kDa chain of the IL-2 receptor complex with Tac antigen (IL-2R/p55(Tac]. Triggering of Fc epsilon RII/CD23 resulted in the enhanced expression of IL-2R/p55(Tac), whereas IL-2 enhanced the expression of Fc epsilon RII/CD23 in some systems. It is suggested that the triggering of cell surface Fc epsilon RII/CD23 by natural ligands is effectively buffered by soluble Fc epsilon RII/CD23 (IgE-BF).
Yodoi
J
J
Institute of Immunology, Faculty of Medicine, Kyoto University, Japan.
Hosoda
M
M
Maeda
Y
Y
Sato
S
S
Takami
M
M
Kawabe
T
T
D000595:Amino Acid Sequence; D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism* / Q000502:physiology; D001483:Base Sequence; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism*; D007143:Immunoglobulin Heavy Chains / Q000378:metabolism*; D007139:Immunoglobulin epsilon-Chains / Q000378:metabolism*; D008969:Molecular Sequence Data; D011961:Receptors, Fc / Q000378:metabolism* / Q000502:physiology; D017455:Receptors, IgE
D000944:Antigens, Differentiation, B-Lymphocyte; D007143:Immunoglobulin Heavy Chains; D007139:Immunoglobulin epsilon-Chains; D011961:Receptors, Fc; D017455:Receptors, IgE; D007073:Immunoglobulin E