To investigate the role of SH-2-containing protein tyrosine phosphatase 1, SHP-1, in IL-4-induced IL-4 receptor (IL-4R) expression, we examined IL-4 receptor α-chain (IL-4Rα) mRNA expression in Na3VO4-treated wild type (WT) spleen cells and measured IL-4R mRNA in IL-4-stimulated spleen cells of viable motheaten mice (mev/mev). It is found that IL-4-induced IL-4R mRNA expression was impaired in Na3VO4-treated WT spleen cells and IL-4-stimulated mev/mev spleen cells. Here we show that the impaired IL-4-induced IL-4RαmRNA expression was due to reduced expression of IL-4R that led to impaired STAT6 signaling. We further demonstrate that reduction of IL-4Rαprotein expression in mev/mev spleen cells was due to alteration in cell compositions. In mev/mev spleen, the percentages of CD4+, CD8+, and CD19+ cells expressing relatively high levels of IL-4R were reduced dramatically while the percentages of Mac-1+ and Gr-1+ cells with relative low levels of IL-4R increased greatly. Despite the profound effect of reduced expression of IL-4R protein, the IL-4RαmRNA expression was comparable in spleen cells of littermate control mice (+/() and mev/mev mice and no differences were found in B cells, T cells, and macrophages, suggesting cell type-specific downregulation of IL-4R expression in macrophages through a posttranscriptional mechanism. Our study suggests that SHP-1 is required for IL-4-meidated function and indirectly regulates IL-4-meidated function in spleen cells by affecting hematopoiesis.