VM8054 Veterinary Histology

Example: Lipofuscin

Author: Dr. Thomas Caceci

This is an example of cells containing lipofuscin, the indigestible residue of the breakdown of cellular material. In this field you see some macrophages, the scavenger cells of the body, at work. They have entered an area in which infection has taken place and are working to remove the dead cells and/or bacteria in the region. The lipofuscin is the brownish-gold pigment visible inside them. Had there been hemorrhage in this region, some of the macrophages would have contained hemosiderin, too. In H&E sections it can be difficult to determine whether the pigment seen is lipofuscin or hemosiderin, but and easy way to distinguish the two is by using a stain for iron such as Prussian Blue; hemosiderin gives a positive reaction with PB and lipofuscin doesn't.

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

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