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interleukin-4 receptor (IL4R) 402 interleukin-4 receptor (IL4R)
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Schematic representation of the interleukin-3 (IL-3) receptor. Schematic
representation of the interleukin-6 (IL-6) receptor. IL-6 receptors of high
affinity are composed of two subunits that are noncovalently associated.
Low-affinity binding of IL-6 to the IL-6Rα chain occurs, but no signal is
produced. The gp130 extracellular domain is composed of an IgSF C to
set domain at the N-terminus. The cytokine receptor-SF domain and four
fibronectin III domains follow. The WSXWS motif is present only in the first
of the fibronectin III domains. The human IL-6Rα chain has five potential
N-linked glycosylation sites, and the gp130 domain has ten.
principal regulator of humoral and adaptive immunity. IL4
induces B cell class switching to IgE and upregulates MHC
class II production. Most studies of IL4 have been in mice,
where it serves as a growth and differentiation factor for B
cells and is a switch factor for synthesis of immunoglobulin
E (IgE). It also promotes growth of a cloned CD4 + T cell
subset. Further properties of murine IL4 include its function
as a growth factor for mast cells and activation factor
for macrophages. It also causes resting B lymphocytes to
enlarge and enhances major histocompatibility complex
(MHC) class II molecule expression. IL4 was previously
termed B cell growth factor I (BCGF-I) and B cell-stimulating
factor 1 (BSF-1). In humans, CD4 + T lymphocytes also
produce IL4, but the human variety has not been shown to
serve as a B cell or mast cell growth factor. Human IL4 also
fails to activate macrophages. Both murine and human IL4s
induce switching of B lymphocytes to synthesize IgE; thus
IL4 may be significant in allergies. Human IL4 also induces
CD23 expression by B lymphocytes and macrophages in
humans. It may play some role in cell-mediated immunity.
It induces differentiation of T h2 cells from naïve CD4 +
precursor cells, stimulates IgE formation by B cells, and
suppresses IFN-γ-dependent macrophage functions.
A ribbon diagram of IL-4 that constitutes a theoretical model of human
IL-4.
Interleukin-4 crystal structure.
interleukin-4 receptor (IL4R)
A structure composed of two major complexes, one of
which is a 140-kDa single chain that constitutes a high
affinity IL4 binding site (IL4Rα). The IL4Rα possesses
pairs of cysteine residues and the WSXWS motif present
in other members of the hematopoietin receptor superfamily,
a classic transmembrane domain, and a 500-amino
acid cytoplasmic domain. The IL4 receptor complex also
contains other polypeptide chains. Following the binding