The RBC's here have stacked together in long chains. This is known as "rouleaux formation" and it happens with increased serum proteins, particularly fibrinogen and globulins. Such long chains of RBC's sediment more readily. This is the mechanism for the sedimentation rate, which increases non-specifically with inflammation and increased "acute phase" serum proteins.

Question: What are some acute phase proteins?

AnswerThese may include C-reactive protein, serum amyloid A, haptoglobin, and fibrinogen. Cytokine activators of acute phase proteins include IL-1 and IL-6.