The Brush Cell

To the Editor:

I thank Lynne Reid and colleagues (1), who recently resurrected our thinking about the pulmonary "brush" cell. Even though this cell type was identified decades ago, essentially nothing is known about its function, as clearly described by the group that met to entertain discussion on the topic (1).

One reason so little is known is the lack of knowledge that the cell even exists. I'm struck by this fact each year when I present a lung microanatomy lecture and quiz to our pulmonary fellows, who can instinctively recognize Type II cells and macrophages but gaze silently at the projection screen in awe of this robust and enigmatic cell (see Figure 1). Before I can start my next sentence, the question always is, "What does it do?" Now I have a recent review to reference. Perhaps this interesting discussion of how little we know (1) will encourage our students and fellows to think about the functions that could be exhibited by such a cell type.

I tend to favor the sensory, even sentinel nature of the cell based on its strategic position in the airways and at duct bifurcations, extensive cytoskeleton. yet sparse distribution (1). For our viewing enjoyment, included is a scanning electron micrograph that I took years ago of two normal human bronchiolar brush cells surrounded by Clara and ciliated cells. Those broad, flat "villi" (it's hard to call them micro-) are highly conserved across species and obviously evolved for a very good reason. Encouraging our trainees to establish that reason might benefit us all.

Conflict of Interest Statement: A.R.B. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript.

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