Enhancement of CD8+ T cell responses by ICOS/B7h costimulation

Area of Science:

• Immunology
• Cellular Biology
• Cancer Research

Background:

• The role of ICOS/B7h costimulatory counterreceptors in CD4(+) T cell responses is established.
• Their regulatory capacity for CD8(+) T cell responses remains largely undetermined.

Purpose of the Study:

• To investigate the function of ICOS/B7h in regulating CD8(+) T cell responses.
• To determine the impact of B7h on both naive and memory CD8(+) T cell responses in a tumor rejection model.

Main Methods:

• Utilized a tumor-rejection model with ectopic B7h expression.
• Compared T cell kinetics, proliferation, and cytokine production (IL-2, IFN-gamma) in vitro for naive and rechallenged 2C-transgenic T cells.
• Assessed CD8(+) T cell responses in the absence of CD4(+) T cells.

Main Results:

• Ectopic B7h expression costimulated CD8(+) T cell-mediated tumor rejection without CD4(+) T cells.
• B7h significantly augmented responses of naive T cells and was highly effective in mobilizing recall responses.
• Rechallenged CD8(+) T cells showed preferential costimulation for IL-2 and IFN-gamma production by B7h.

Conclusions:

• ICOS/B7h counterreceptors enhance secondary CD8(+) T cell responses in vivo.
• The pathway plays a significant role in adaptive immunity, particularly in memory CD8(+) T cell function and tumor immunity.