CD28 is expressed by macrophages with anti-inflammatory potential and limits their T-cell activating capacity

Area of Science:

• Immunology
• Cell Biology

Background:

• CD28 is typically known as a T lymphocyte-specific co-stimulatory molecule.
• Previous research indicated CD28 mRNA expression in M-CSF-dependent anti-inflammatory macrophages (M-MØ).

Purpose of the Study:

• To investigate CD28 cell surface expression and function in macrophages.
• To explore the regulation of macrophage CD28 expression.
• To assess the role of CD28 in macrophage-mediated immune responses.

Main Methods:

• Flow cytometry to assess CD28 surface expression on M-MØ and GM-CSF-dependent macrophages.
• Analysis of CD28 expression in tumor-associated macrophages and macrophages from rheumatoid arthritis patients.
• In vitro studies using mouse bone marrow-derived M-MØ, including Cd28 knockout (Cd28KO) models.
• Stimulation with anti-CD28 antibodies to assess ERK1/2 phosphorylation.
• Functional assays measuring T cell proliferation and cytokine production (IL-6).
• Transcriptome analysis of Cd28KO versus wild-type (WT) M-MØ.

Main Results:

• CD28 cell surface expression is higher on M-MØ compared to GM-CSF-dependent macrophages.
• Macrophage CD28 expression is regulated by MAFB and activin A.
• CD28 is present in tumor-associated macrophages and synovial fluid macrophages from rheumatoid arthritis patients.
• Anti-CD28 antibodies induce ERK1/2 phosphorylation in mouse M-MØ.
• Cd28KO M-MØ show enhanced capacity to activate OVA-specific CD4+ T cell proliferation and increased LPS-induced IL-6 production.
• Transcriptome analysis reveals significant differences in IFN response, inflammatory response, and TGF-β signaling pathways between Cd28KO and WT M-MØ.

Conclusions:

• CD28 expression is a characteristic of anti-inflammatory macrophages.
• Defective CD28 expression in macrophages alters gene expression profiles and macrophage functionality.
• CD28 on macrophages represents a potential therapeutic target for immunotherapy.