Macrophage and multinucleated giant cell classification

The purpose of this chapter is to provide an overview of macrophage subtype and multinucleated giant cell classification with a specific discussion of their role(s) in response to particulates and other foreign bodies. Topics covered for the different subtypes include the following: environmental factors involved in their generation, functional characterization, disease associations, and interactions with particulates. This chapter is separated into three major parts. The first portion describes the normal structure and functions of the macrophage. Second, the currently published macrophage subsets are outlined. The classifications included in the discussion are based on function ("M" polarization) rather than anatomical position (tissue-specific macrophages - Kupffer cells, alveolar macrophages, etc.). As shown in Fig. 1.1, the ontogeny of the various types of macrophages being discussed in this chapter depends on the pathway of activation. The third major section focuses on multinucleated giant cells, which are formed by fusion of individual macrophages. The ontogeny of each subset will be discussed and the current literature regarding particulate/foreign-body interaction will be reviewed.