A 42-year-old man with a history of intravenous drug use presents to the emergency department with fever, malaise, and a new cardiac murmur. On examination, you notice flat, non-tender erythematous lesions on his palms and soles. The structure marked **B** in the diagram represents the characteristic appearance of these lesions. Which of the following best describes the pathophysiological basis of the lesions marked **B**?