Graduation Year

2008

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Molecular Medicine

Major Professor

Thomas W. Klein, Ph.D.

Keywords

LPS, Legionella, Bacillus, DCs, Infection

Abstract

Bacillus anthracis produces lethal toxin (LT) and edema toxin (ET) and they suppress the function of LPS-stimulated dendritic cells (DC). Because DCs respond differently to various microbial stimuli, we compared toxin effects in bone marrow DCs stimulated with either LPS or Legionella pneumophila (Lp). DCs were enriched with GM-CSF for 9 days, purified by positive selection, and treated with toxins for 6h; cells were then stimulated with either LPS or Lp-infection for 24h. DC cytokine production and maturation marker expression varied depending upon cell stimulus and the mouse strain used. LT but not ET was more toxic for cells from BALB/c than from C57BL/6 (B6) as measured by 7-AAD uptake; however, ET suppressed CD11c expression. LT suppressed IL-12, IL-6, and TNF-a in cells from BALB/c and B6 mice but increased IL-1ß in LPS-stimulated cultures. ET also suppressed IL-12 and TNF-a but increased IL-6 and IL-1ß in Lp-stimulated cells from B6. Regarding maturation marker expression, LT increased MHCII and CD86 while suppressing CD40 and CD80; ET, on the other hand, generally decreased marker expression across all groups. We conclude that the modulation of cytokine production by anthrax toxins is dependent on variables including the source of the DCs, the type of stimulus and cytokine measured, and the individual toxin tested. However, LT and ET enhancement or suppression of maturation marker expression is more related to the marker studied than the cell stimulus or cell source. Anthrax toxins are not uniformly suppressive of DC function but instead can increase function under defined conditions.

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