IL-15 regulates CD8+ T cell contraction during primary infection

Area of Science:

• Immunology
• Cellular Biology
• Infectious Diseases

Background:

• Following acute infection, antigen-specific T cells undergo expansion and contraction, with a subset persisting as memory cells.
• Interleukin-15 (IL-15) is known for its role in memory CD8+ T cell maintenance.
• The specific function of IL-15 during the CD8+ T cell contraction phase remains unclear.

Purpose of the Study:

• To investigate the role of IL-15 in the contraction phase of effector CD8+ T cells after microbial infection.
• To determine if IL-15 influences the apoptosis of effector CD8+ T cells during contraction.

Main Methods:

• Utilized an adoptive transfer system with OT-I cells in IL-15 knockout (KO) and transgenic (Tg) mice.
• Infected mice with recombinant Listeria monocytogenes expressing ovalbumin (OVA).
• Administered recombinant IL-15 (rIL-15) in vivo during the contraction phase and analyzed Bcl-2 expression.

Main Results:

• Effector OT-I cell survival during contraction was critically dependent on IL-15.
• IL-15 KO mice showed reduced OT-I cell numbers, while IL-15 Tg mice maintained higher levels.
• rIL-15 administration in KO mice inhibited contraction and upregulated Bcl-2 expression; enforced Bcl-2 expression protected cells from apoptosis.

Conclusions:

• IL-15 plays a vital role in protecting effector CD8+ T cells from apoptosis during the contraction phase post-infection.
• This protection is mediated through the induction of anti-apoptotic molecules, such as Bcl-2.
• Findings highlight IL-15's significance beyond memory cell maintenance, extending to effector cell survival.