consistent with an abscess.Which of the following actions by inflammatory cells is most likely to produce this CT finding? A.Formation of nitric oxide by macrophages B.Formation of transforming growth factor-B by macrophages C.Generation of prostaglandin by endothelium D.Production of interferon-y by lymphocytes E.Release of lysosomal enzymes from neutrophils Ans:E Nongenital heart defectsh-o-ef shumting predispo se ly S ausing gener granulation tissue here because we see extensive necrotic debris more likely due to powerful lysosomal enzymes. TGF-beta secretion by macrophages actually turns off the inflammatory response in preparation for healing.Prostaglandins have many functions but are not related to the direct actions of the microbial-killing inflammatory cells.Interferon-gamma is a cytokine released by lymphocytes in response to viral or intracellular bacterial infections.It is less likely to cause the extensive necrosis evident in this patient. -6- 6 - consistent with an abscess. Which of the following actions by inflammatory cells is most likely to produce this CT finding? A. Formation of nitric oxide by macrophages B. Formation of transforming growth factor-B by macrophages C. Generation of prostaglandin by endothelium D. Production of interferon-γ by lymphocytes E. Release of lysosomal enzymes from neutrophils Ans: E Congenital heart defects with right-to-left shunting predispose patients to brain abscesses. Neutrophils release lysosomal enzymes (“respiratory burst”) to kill invading microorganisms, causing general liquefactive necrosis. Over time, granulation tissue and neovascularization surround the infection, hence the ring-enhancing lesion evident on CT. Nitric oxide can be secreted as a free radical that causes microbial death via DNA damage. It is not the best choice here because we see extensive necrotic debris more likely due to powerful lysosomal enzymes. TGF-beta secretion by macrophages actually turns off the inflammatory response in preparation for healing. Prostaglandins have many functions but are not related to the direct actions of the microbial-killing inflammatory cells. Interferon-gamma is a cytokine released by lymphocytes in response to viral or intracellular bacterial infections. It is less likely to cause the extensive necrosis evident in this patient