Identification of cell types and quantification of lesion composition

Many different cell types have been identified in atherosclerotic plaques, including endothelial cells, smooth muscle cells, monocytes, monocyte-derived macrophages, lymphocytes, and mast cells. Examining the role each cell type plays in the formation and pathophysiology of atherosclerotic plaques relies upon the identification of these cells within plaques and early plaque-like structures, which in turn depends on their expression of recognizable and stable morphological characteristics. Cell-type characterization was limited in early studies to light microscopy, and then electron microscopy increased the number of different cell types identified. There is still substantial information to be gained by the use of these methods alone, but more recently the increasing use of immunohistochemistry with a panel of cell-type-specific antibodies has simplified and expanded these earlier methods (1). There are now examples of commercially available antibodies for most cell types thought to be involved in the atherosclerotic process. The protocol for utilizing these antibodies for cell identification requires three steps: tissue collection, sectioning, and staining; this chapter will deal in detail with the last only.