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Splenic red pulp macrophages eliminate the liver-resistant Streptococcus pneumoniae from the blood circulation of

Haoran An1,2,3, Yijia Huang4, Zhifeng Zhao5

  • 1Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China.

Science Advances
|March 12, 2025
PubMed

Insights

The spleen acts as a backup immune organ, clearing bacteria like Streptococcus pneumoniae that evade the liver. Splenic macrophages, supported by natural antibodies and complement, are crucial for this defense.

Area of Science:

  • Immunology
  • Infectious Diseases
  • Microbiology

Background:

  • Encapsulated bacteria cause significant human illness and death.
  • Kupffer cells in the liver clear many bacteria but fail against high-virulence strains.
  • Streptococcus pneumoniae is a leading cause of invasive bacterial infections.

Purpose of the Study:

  • To investigate the spleen's role in clearing liver-resistant encapsulated bacteria.
  • To identify the immune cells and mechanisms involved in splenic bacterial clearance.
  • To explain the increased susceptibility of asplenic individuals to pneumococcal infections.

Main Methods:

  • Utilized asplenic mouse models to assess bacterial clearance.
  • Performed immunologic and genetic analyses to identify key phagocytes.
  • Investigated the role of natural antibodies and the complement system.

Main Results:

  • Asplenic mice showed impaired control of liver-resistant pneumococci.
  • Splenic red pulp macrophages were identified as primary phagocytes.
  • Natural antibodies targeting phosphocholine and complement were essential for clearance.

Conclusions:

  • The spleen serves as a critical backup immune organ for bacterial clearance.
  • Splenic red pulp macrophages mediate innate immunity against certain bacteria.
  • Findings explain asplenic individuals' susceptibility and inform vaccine development.

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