Sepsis leads to a reduced antigen-specific primary antibody response

Area of Science:

• Immunology
• Infectious Disease

Background:

• Sepsis is characterized by immunosuppression, impaired cytokine production, and susceptibility to secondary infections.
• Polymicrobial septic peritonitis induced by cecal ligation and puncture (CLP) in mice mimics human sepsis conditions.

Purpose of the Study:

• To investigate the impact of sepsis on B-cell responses and antigen-specific antibody production.
• To elucidate the mechanisms underlying immune dysregulation in septic mice.

Main Methods:

• Induction of polymicrobial septic peritonitis using cecal ligation and puncture (CLP) in mice.
• Analysis of B-cell populations, immunoglobulin levels (IgG, IgM), and memory B-cell responses.
• Assessment of splenocyte activation, myeloid cell function (arginase, NO production), and dendritic cell (DC) antigen presentation.
• Evaluation of T-cell responses, including cytokine production (IFN-γ, Th1, Th2) and regulatory T-cell (Treg) populations.
• Adoptive transfer experiments with naive immune cells.

Main Results:

• CLP significantly impaired antigen-specific primary antibody production while increasing total IgG and IgM levels and memory B-cell responses.
• Activated CD11b(+) splenocytes showed increased arginase and nitric oxide (NO) production.
• Dendritic cells exhibited reduced IL-12 production and altered antigen presentation, leading to decreased CD4(+) T-cell proliferation but enhanced IFN-γ production.
• CD4(+) T cells from septic mice showed reduced Th1 and Th2 cytokine production, with an increase in Treg cells.
• B-cell populations shifted towards mature B cells, with a decrease in immature B cells.

Conclusions:

• Sepsis profoundly disrupts adaptive immune responses, specifically impairing antigen-specific antibody production despite alterations in B-cell populations and immunoglobulin levels.
• Immune dysregulation involves myeloid cell activation, impaired dendritic cell function, and altered T-cell polarization, contributing to the compromised antibody response.
• Adoptive transfer of naive immune cells did not restore the antigen-specific antibody response, suggesting complex multifactorial immune deficits in sepsis.