Alternative splicing generates putative soluble CD83 proteins that inhibit T cell proliferation

Area of Science:

• Immunology
• Molecular Biology

Background:

• CD83 is expressed on mature dendritic cells and activated lymphocytes, playing a role in T cell development.
• The function and generation of soluble CD83 (sCD83) in the periphery remain largely unknown.
• Soluble CD83 has been detected in serum, but its biological significance is unclear.

Purpose of the Study:

• To investigate the different CD83 transcripts in unstimulated peripheral blood mononuclear cells (PBMCs).
• To analyze the generation and function of soluble CD83 (sCD83) isoforms.
• To explore the role of sCD83 in immune regulation.

Main Methods:

• Identification and sequence analysis of CD83 transcripts in PBMCs.
• Stimulation of PBMCs with PHA, TNF-alpha, and LPS.
• Analysis of CD83 transcript expression levels.
• Translation of the smallest CD83 splice product and production of recombinant sCD83.
• Assessment of recombinant sCD83's effect on T cell proliferation in mixed lymphocyte reactions (MLRs).

Main Results:

• Four distinct CD83 transcripts were identified in unstimulated PBMCs.
• The longest transcript codes for transmembrane CD83 (CD83-TM); smaller transcripts code for putative soluble CD83 proteins.
• PBMC stimulation altered the expression of CD83 transcripts, up-regulating full-length and down-regulating some splice variants.
• The smallest CD83 splice product was efficiently translated, and recombinant sCD83 significantly inhibited T cell proliferation in MLRs.

Conclusions:

• Soluble CD83 is produced from splice variants of CD83 in PBMCs.
• Constitutive production of sCD83 may regulate immune homeostasis in the periphery.
• sCD83 exhibits inhibitory effects on T cell proliferation, highlighting its potential immunomodulatory function.