A patient with chronic serum sickness develops fever, joint pain, and a rash several days after receiving an injection of foreign serum proteins. Laboratory analysis reveals deposition of antigen–antibody complexes in small blood vessels and activation of complement. This condition is most consistent with which type of hypersensitivity reaction?

The trigger for Type III hypersensitivity reactions is:

A researcher is studying the pathogenesis of serum sickness, a classic type III hypersensitivity reaction. The following events are observed during the reaction:

1. Complement fragments promote chemotaxis of inflammatory cells

2. Antibodies bind soluble antigens to generate circulating immune complexes

3. Neutrophils release proteolytic enzymes that injure surrounding tissue

4. Small immune complexes become trapped in vessel walls and activate complement

5. Circulating immune complexes avoid efficient clearance by phagocytes

Which sequence correctly represents the progression of these events?

During a rheumatology lecture, a professor asks students to identify the joint pattern that most strongly suggests early rheumatoid arthritis. Which of the following locations is classically involved in the early stages of this disease?

A medical student studying autoimmune diseases learns that systemic lupus erythematosus is associated with the production of anti–double‑stranded DNA antibodies. These antibodies recognize antigens found primarily in which cellular location?