A subset of anti-CD21 antibodies promote the rescue of germinal center B cells from apoptosis

✍ Scribed by Jean-Yves Bonnefoy; Sybille Henchoz; Deborah Hardie; Michelle J. Holder; John Gordon

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 483 KB
• Volume: 23
• Category: Article
• ISSN: 0014-2980
• DOI: 10.1002/eji.1830230432

✦ Synopsis

Expression of a 32-kDa ligand for the CD40 antigen on activated human T lymphocytes

To identify the ligand(s) of the human CD40 antigen, a cDNA encoding the extracellular domain of the CD40 antigen was fused to a cDNA encoding the constant region (Fc) of human IgG1. The CD40-Fc fusion protein was able to specifically bind to CD4+ and various CD8+ Tcell clones activated with immobilized anti-CD3. The 1251-labeled CD40-Fc fusion protein bound anti-CD3 activated CD4+ T cell clone (MT9) with an equilibrium dissociation constant (Kd) of 10-20 nM. The human CD40-binding protein expressed on the cell surface of activated T lymphocytes is a monomeric protein of = 32 kDa. Minor components of 29 kDa and 17 kDa were also detected. A small proportion of CD4+ and CD8+ blood mononuclear T cells activated by anti-CD3 expressed the CD40 ligand but its detection was best observed following depletion of B cells. Addition of B cells to purified T cells abolished the binding of CD40-Fc obtained after anti-CD3 activation.