Cytokine Secretion by Macrophages

Cytokine Secretion by Macrophages

  • Macrophages can be activated by various stimuli, including microbes and their products, immune complexes, cytokines, injured tissue components (alarmins), sensitized T cells, etc.
  • Activated macrophages possess an increased number of lysosomes and produce a broad set of cytokines.
  • The main macrophage cytokines (monokines) are IL-1, IL-6, IL-8, IL-12, IL-18, α-TNF, prostaglandins, leukotrienes, and some others.
  • Pro-inflammatory cytokines (presumably IL-1, IL-6, IL-12, IL-18, α-TNF) have a wide range of biological activity.
  • They cause febrile reactions with fever and chills. Also, they participate in the activation of lymphoid cells (predominantly of Th1), resulting in the release of other pro-inflammatory cytokines (IL-2, γ-interferon, etc.) with progressive tissue inflammation.
  • Redundant cytokine production, especially after bacterial endotoxin exposure, can lead to septic shock with fever, collapse, and inner organ failure.
  • The macrophages, stimulating inflammatory reactions, are termed as classically activated macrophages.
  • They were designated as M1 macrophage subpopulation. Together with potent microbicidal activity, in some situations they may trigger an autoimmune inflammatory response (e.g., in rheumatoid arthritis or multiple sclerosis).
  • Alternatively activated macrophages (or M2 macrophages) are stimulated by anti-inflammatory cytokines IL-4, IL-10, and TGF-β, as well as by-products of fungi and helminth infections. Therefore, they take part in anti-parasite immunity. Also, they are engaged in allergic reactions.
  • M2 cells produce low amounts of IL-12, but high levels of IL-10, thus maintaining tissue anti-inflammatory state.

Cytokine Secretion by Macrophages

References

  1. https://www.researchgate.net/publication/267739405_Macrophage_Cytokines_Involvement_in_Immunity_and_Infectious_Diseases