Fig. 5

ILT-4 is a receptor inducibly expressed on activated human CD4⁺ T cells for SEMA4A. a Expression of ILT-4 mRNA was induced in activated CD4⁺ T cells. The expression levels of ILT-4 mRNA were detected by real-time PCR in freshly purified human naive CD4⁺T cells or Tn cells activated with immobilized OKT3 and soluble anti-CD28 mAb for the indicated day1, day 2, day 3, and day 4, respectively. The relative fold differences in gene expression between samples are indicated on the y-axis. Error bars represent the s.e.m. of different wells. Data represent one of four independent experiments. b SEMA4A-Fc blocks the binding of anti-ILT-4 mAb to activated CD4⁺ T cells. Purified naive CD4⁺ T cells were activated with immobilized anti-CD3, anti-CD28 mAb for 1 day. Cells were stained with isotype control antibody (filled area), anti-ILT-4 mAb plus hIgG (dashed line), or an excess of SEMA4A-Fc plus anti-ILT-4 mAb (full line), and analyzed by flow cytometry. Data represent one of five independent experiments. c ILT-4-Fc blocks the binding of SEMA4A-Fc to activated CD4⁺ T cells. Purified naive CD4⁺ T cells were activated with immobilized anti-CD3, anti-CD28 mAbs for 1 day. Cells were stained with hIgG (filled histogram), SEMA4A-Fc (dashed line) or an excess of ILT-4-Fc and SEMA4A-Fc (full line), and analyzed by flow cytometry. Data represent one of five independent experiments. d IL-4 enhances ILT-4 expression on activated T cells. Purified naive CD4⁺ T cells were activated with immobilized anti-CD3 plus anti-CD28 mAbs in the absence or presence of IL-4 at the indicated concentrations for 7 days. ILT-4 expression was detected by flow cytometry. Open histograms represent the staining with anti-ILT-4 mAb; filled histograms represent the isotype. Data represent one of five independent experiments