Polymicrobial Sepsis Impairs Antigen-Specific Memory CD4 T Cell-Mediated Immunity.

Area of Science:

• Immunology
• Infectious Disease
• T cell biology

Background:

• Sepsis survivors experience prolonged immune dysfunction and increased susceptibility to secondary infections.
• CD4 T cells are crucial for protective immunity, and their dysfunction compromises the immune system.
• The cecal ligation and puncture (CLP) model mimics sepsis in mice to study its immunological consequences.

Purpose of the Study:

• To investigate the impact of sepsis on endogenous antigen-specific memory CD4 T cells.
• To assess the functional recovery and protective capacity of these memory cells post-sepsis.
• To understand how sepsis-induced alterations in memory CD4 T cells contribute to post-sepsis immunoparalysis.

Main Methods:

• Utilized the CLP mouse model to induce sepsis.
• Generated antigen-specific memory CD4 T cells using attenuated Listeria monocytogenes (Lm-2W) and Lm-OVA.
• Assessed memory CD4 T cell numbers, proliferation, cytokine production, and protection against secondary Salmonella enterica (Se-2W) challenge.

Main Results:

• Sepsis transiently reduced memory CD4 T cell numbers but caused prolonged functional impairment, including reduced recall responses.
• Sepsis survivors exhibited increased pathogen burden when challenged with a secondary infection, indicating impaired protective immunity.
• Similar functional deficits and reduced protection were observed in OVA-specific memory CD4 T cells.

Conclusions:

• Cecal ligation and puncture-induced sepsis significantly alters the number and function of antigen-specific memory CD4 T cells.
• These alterations in memory CD4 T cells contribute to the long-lasting immune dysfunction observed in sepsis survivors.
• The findings highlight a critical mechanism underlying sepsis-associated immunoparalysis and increased secondary infection risk.