Author: Dr. Thomas Caceci
Salivary gland; H&E stain, 400x
In this higher magnification image the nature of the lipofuscin inclusions in the macrophages is easily seen. The granular appearance of the inclusion, and its presence in some cells but not others, is a clue to its nature and origin. Lipofuscin inclusions are formed by the fusion of a primary lysozome and a phagocytic vesicle. The combined inclusion vesicles will be of varying size, and also of varying density. Note also that the nucleus of the large macrophage in the upper left corner of the image is pretty well obscured by the lipofuscin inclusions. This is a very active cell. Newly-recruited macrophages just differentiating in the region would have fewer granules in them. The density of the inclusions and their distribution will also vary somewhat depending on what it is the macrophage has engulfed and what's being broken down in the cytoplasm.
Salivary gland; H&E stain, 1000x