Abrogation of streptococcal pyrogenic exotoxin B-mediated suppression of phagocytosis in U937 cells by Cordyceps sinensis mycelium via production of cytokines

Food Chem Toxicol. 2007 Feb;45(2):278-85. doi: 10.1016/j.fct.2006.08.017. Epub 2006 Sep 1.


Streptococcal pyrogenic exotoxin B (SPE B) is a virulent factor in group A streptococcal infection. We previously showed that SPE B reduced phagocytosis in human monocytic U937 cells. Here we show that the mycelium extract of Cordyceps sinensis (CS), a Chinese immunomodulatory herbal medicine, increased phagocytosis in U937 cells. Neither heat nor trypsin pretreatment prevented CS extract from causing this increase. Further studies indicated that SPE B-mediated suppression of U937 cell phagocytic activity was abrogated by CS extract. Factors in the conditioned medium from CS-extract-treated U937 cells were responsible for blocking the SPE B-mediated suppression of phagocytosis. Heating the conditioned medium eliminated the increase, which suggested that the U937-cell protein products augmented phagocytosis. Analyzing cytokine mRNA expression of U937 cells revealed increases in interferon-gamma (IFN-gamma), interleukin (IL)-12 p35 and p40, and tumor necrosis factor-alpha (TNF-alpha), but not in IL-1beta, IL-6, or IL-8. Treating U937 cells with anti-IFN-gamma, IL-12, and TNF-alpha antibodies also eliminated the conditioned medium-induced increase in phagocytosis. Taken together, SPE B inhibited phagocytosis, but CS mycelium extract abrogated this inhibition by causing cytokine production.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / antagonists & inhibitors
  • Bacterial Proteins / toxicity*
  • Cordyceps / chemistry
  • Cordyceps / immunology*
  • Cordyceps / metabolism
  • Cytokines / biosynthesis*
  • Cytokines / immunology
  • Cytokines / pharmacology
  • Exotoxins / antagonists & inhibitors
  • Exotoxins / toxicity*
  • Fluorescence
  • Hot Temperature
  • Humans
  • Immunosuppressive Agents / pharmacology*
  • Mycelium / chemistry
  • Mycelium / immunology
  • Mycelium / metabolism
  • Phagocytosis / drug effects*
  • Streptococcus pyogenes / metabolism
  • Trypsin / pharmacology
  • U937 Cells


  • Bacterial Proteins
  • Cytokines
  • Exotoxins
  • Immunosuppressive Agents
  • erythrogenic toxin
  • Trypsin