Endogenously produced IL-4 nonredundantly stimulates CD8+ T cell proliferation

Area of Science:

• Immunology
• Cell Biology

Background:

• Cytokine receptor common gamma-chain-associated cytokines (IL-2, IL-7, IL-15) regulate T cell proliferation and survival.
• Interleukin-4 (IL-4) was traditionally considered to primarily influence T cell quality, not quantity.

Purpose of the Study:

• To investigate the role of endogenously produced IL-4 in CD8(+) T cell responses.
• To determine if IL-4 directly impacts T cell proliferation and survival.

Main Methods:

• Experiments were conducted in BALB/c and C57BL/6 mice.
• Both naive and memory/activated phenotype CD8(+) T cells were analyzed.
• The study examined IL-4's independence from IL-7 and IL-15 and its dependence on MHC class I stimulation.

Main Results:

• Endogenously produced IL-4 was found to be a potent stimulator of CD8(+) T cell proliferation in antigen- and pathogen-induced responses.
• IL-4 stimulated both naive and memory/activated phenotype CD8(+) T cells, with greater effect on the latter.
• IL-4's mitogenic effect on naive CD8(+) T cells required MHC class I-dependent stimulation and was independent of IL-7 and IL-15.

Conclusions:

• Endogenously produced IL-4 is a direct, nonredundant regulator of CD8(+) T cell proliferation.
• IL-4 plays a significant role in the quantitative aspects of CD8(+) T cell immunity, in addition to its known qualitative effects.
• These findings broaden the understanding of IL-4's function in adaptive immunity.