Scanning electron micrograph of two rod-shaped bacilli of Klebsiella pneumoniae (colorized red), which can cause pneumonia and bloodstream infections. (Credit: David Dorward/National Institute of Allergy and Infectious Diseases)
Scanning electron micrograph of spheroid-shaped methicillin-resistant Staphylococcus aureus (MRSA) bacteria (colorized yellow) surrounded by cellular debris (colorized orange). (Credit: National Institute of Allergy and Infectious Diseases)
Mast cell activation. (a) Multiple stimuli can activate mast cells. (b) Activated mast cells produce mediators and proteins that can influence the outcome of an immune response or its associated tissue changes.