A native soluble form of CTLA-4.

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is a key immunoregulatory receptor on T and B lymphocytes.
• CTLA-4 interacts with B7 family molecules, influencing immune responses.
• Understanding CTLA-4's diverse forms is crucial for immunomodulation.

Purpose of the Study:

• To identify and characterize alternatively spliced CTLA-4 messenger RNAs (mRNAs).
• To investigate the presence and function of soluble CTLA-4 (sCTLA-4) in biological systems.
• To explore the regulation of CTLA-4 splicing during immune activation.

Main Methods:

• Reverse transcription polymerase chain reaction (RT-PCR) was used to detect alternatively spliced CTLA-4 transcripts.
• Analysis was performed on mRNA from human, mouse, and rat hematolymphoid tissues, including resting T cells and B cells.
• Recombinant sCTLA-4 was used to assess its binding and immunomodulatory properties in vitro.

Main Results:

• Alternatively spliced CTLA-4 mRNAs lacking the transmembrane domain were identified in various immune cells.
• These transcripts were found in resting CD4+ and CD8+ T cells, as well as B cells.
• Immune cell activation led to a relative decrease in the alternative transcript compared to the full-length transcript.
• Recombinant sCTLA-4 demonstrated B7-binding capacity and inhibited the mixed leukocyte response, indicating immunomodulatory activity.
• Immunoreactive material consistent with a native soluble form of CTLA-4 was detected in human serum.

Conclusions:

• The study reveals the existence of alternatively spliced CTLA-4 variants that can generate soluble forms.
• These soluble CTLA-4 molecules possess functional immunomodulatory properties.
• The findings suggest a role for soluble CTLA-4 in regulating immune responses and its presence in human serum.