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Figure 2 Photomicrographs of a carotid atherosclerotic plaque removed by carotid endarterectomy from a patients who suffered a major stroke. A vulnerable plaque characterized by a large lipidic-necrotic core, a thin fibrous cap (A, Movat pentachrome, 4x) associated to a heavy inflammatory infiltrate constituted mainly by macrofagic foam cells, CD68-positive (B, 10x). A strong positive reaction for pregnancy-associated protein-A was observed (C, 20x). (D, 10x and G, 20x) show CD68 antibody revealed by streptavidin-Texas Red fluorescent conjugate. (E, 10x and H, 20x) Show pregnancy-associated protein-A reaction revealed by streptavidin-fluorescin conjugate. Two dimension confocal analysis of the two fluorochromes (F and I) clearly showed a strong and diffuse positive reaction for pregnancy-associated protein-A in macrophagic cells (concordant double positivity appears as a yellow stain). (K) Shows confocal analysis of the two fluorochromes, smooth muscle actin immunostain (red) and pregnancy-associated protein-A stain (green). Smooth muscle cells observed in this plaque gave rise to a strong positive reaction for pregnancy-associated protein-A (yellow stain). (L) Shows confocal analysis of the two fluorochromes, CD3 immunostain (red) and pregnancy-associated protein-A stain (green). Almost all T lymphocytes (red) observed were negative for pregnancy-associated protein-A in plaques where a diffuse positive reaction was observed (green). Only occasional T lymphocytes were pregnancy-associated protein-A-positive (double positivity, yellow stain, arrow).