Recombinant human CD40 ligand stimulates B cell proliferation and immunoglobulin E secretion

Area of Science:

• Immunology
• Molecular Biology

Background:

• CD40 signaling is vital for B lymphocyte proliferation and differentiation.
• Previous identification of murine CD40 ligand (mCD40-L) with in vitro biological activity.

Purpose of the Study:

• To isolate and characterize the human homologue of mCD40-L (hCD40-L).
• To investigate the expression pattern and biological function of hCD40-L in B cell activation.

Main Methods:

• Isolation of hCD40-L cDNA from activated peripheral blood T cells using crosshybridization.
• Amino acid sequence prediction and comparison with mCD40-L.
• Northern blot and FACS analysis for expression studies.
• In vitro assays using transfected cells to assess B cell proliferation and immunoglobulin secretion.

Main Results:

• hCD40-L is a 261 amino acid type II membrane protein with 78% amino acid identity to mCD40-L.
• hCD40-L expression is restricted to T lymphocytes, predominantly on CD4+ T cells.
• Transfected hCD40-L induced human B cell proliferation without costimuli.
• hCD40-L, with IL-4, induced immunoglobulin E secretion from purified human B cells.

Conclusions:

• The human CD40 ligand (hCD40-L) has been identified and characterized.
• hCD40-L plays a significant role in T cell-mediated B cell activation, proliferation, and immunoglobulin secretion.
• hCD40-L is a key mediator in immune responses involving B lymphocytes.