生物
受体
分子生物学
23号公路
B细胞
白细胞介素4
细胞生物学
抗体
免疫学
细胞因子
免疫球蛋白E
生物化学
作者
C E Zuber,J P Galizzi,Alain Vallé,N Harada,M Howard,Jacques Banchereau
标识
DOI:10.1002/eji.1830200314
摘要
Abstract Human interleukin 4 (IL 4) up‐regulates the expression of CD23 on both resting and “ in vivo ” activated B cells but induces proliferation and/or differentiation only on “ in vitro ” activated B lymphocytes. Resting B cells express 360 high‐affinity IL 4 receptors (R) per cell (K d = 25–75 pM). Activation of resting B cells with anti‐IgM antibody or Staphylococcus aureus Cowan I (SAC) results in a two‐to‐threefold increase of IL 4R number without alteration of IL 4R affinity for IL 4. Flow cytometric analysis of biotinylated IL 4 binding shows that IL 4R expression is up‐regulated on virtually all anti‐IgM‐stimulated B cells, but only on a subpopulation of larger cells among SAC‐activated B lymphocytes. Culturing cells for 40 h with optimal concentrations of IL 4 does not significantly affect IL 4R levels on resting and anti‐IgM‐preactivated B lymphocytes but triples IL 4R levels on SAC‐preactivated B cells. Removal of IL 4 from cell cultures results in a two‐to‐fourfold increase of IL 4R levels 2 h later, suggesting an increase in IL 4R turnover. Resting and activated B cells degrade 125 1‐labeled IL 4 at 37 °C. Sodium dodecyl sulfate‐polyacrylamide gel electrophoretic analysis of IL 4 binding molecules on resting, “ in vivo ” activated and anti‐IgM‐activated B cells reveals the same three species of 130, 80‐75, 70‐65 kDa. Thus, IL 4 displays its different biological activities on resting and activated B cells through IL 4R of the same affinity, gross biochemical structure and ability to mediate IL 4 degradation.
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