Monocyte:T-cell interaction regulates human T-cell activation through a CD28/CD46 crosstalk

Area of Science:

• Immunology
• Cellular Biology

Background:

• T-cell activation requires T-cell receptor and costimulatory molecule engagement.
• CD28 is a key costimulator, while CD46 also costimulates T cells, promoting a Type 1 regulatory (Tr1) phenotype and IL-10 secretion.
• Proteolytic cleavage of CD46 is crucial for T-cell activation and IL-10 production.

Purpose of the Study:

• To investigate how cell-cell interactions within peripheral blood mononuclear cells (PBMCs) modulate the CD46 costimulatory pathway.
• To elucidate the role of monocytes in regulating CD46-mediated T-cell activation and differentiation.

Main Methods:

• Coculture of CD4(+) T cells with autologous monocytes.
• Analysis of CD46 downregulation, CD69 expression, and IL-10 secretion.
• Blocking of the CD28: CD86 pathway and concomitant ligation of CD28 and CD46.

Main Results:

• Monocyte: T-cell cocultures impaired CD46-mediated T-cell differentiation and coactivation.
• Reduced surface CD46 downregulation, lower CD69 induction, and decreased IL-10 secretion were observed in cocultures.
• Blocking CD86 partially restored CD69 expression and cytokine secretion, indicating CD28: CD86 pathway regulation of CD46.
• Direct ligation of CD28 and CD46 modulated CD46 expression and cytokine production.

Conclusions:

• A crosstalk exists between the CD28 and CD46 costimulatory pathways in human T cells.
• Monocytes play a significant role in regulating CD46-mediated T-cell activation and differentiation.
• These findings offer novel insights into the intricate regulation of human T-cell activation.