A 67-year-old homeless man is brought to the emergency department after being found behind a neighborhood bar in freezing weather.On arrival,he has a shaking chill,fever,and cough productive of blood-tinged sputum.A chest radiograph shows lobar consolidations consistent with bacterial pneumonia.Blood cultures are positive for Streptococcus pneumoniae.Which of the following molecular patterns recognized by Toll-like receptors expressed on the surface of this patient's phagocytes is important for activating his innate immune system against this gram-positive bacterial infection?

Question

Quizplus · Accepted Answer

Gram-positive bacteria contain cell walls rich in peptidoglycan.When shed by bacteria such as Streptococcus pneumoniae,peptidoglycan serves as a ligand that binds Toll-like receptor 2 (TLR2),stimulating an innate immune response.The other choices listed are also ligands that stimulate TLRs,but they are not present in gram-positive bacteria.Double-stranded RNA is found in replicating viruses,lipopolysaccharide (LPS)is a component of the outer cell wall of gram-negative bacteria,and both lipoarabinomannan and phosphatidylinositol dimannoside are present in mycobacteria.

A 67-Year-Old Homeless Man Is Brought to the Emergency Department