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Figure 1 a, Frozen section of part of an atherectomy specimen obtained from a patient with unstable angina (group 2). The section is immunodouble-stained for macrophages (anti-CD68) in red and for smooth muscle cells (anti-alpha actin) in blue. The boxed area is enlarged in b through d. Original magnification x30. b, Inflammatory area containing closely packed macrophages (red) and sparse smooth muscle cells (blue). c, Adjacent section stained for mast cells (antitryptase). d, Adjacent serial section stained for T lymphocytes (anti-CD3). Original magnification b through d, x90.