Cell diameter 21 um 9.3 to 30 um · low end human blood monocytes; upper end not attributable to a measurement · mean cell volume by Coulter counter, converted to a sphere-equivalent diameter · Nibbering PH et al. 1990, J Immunol Methods; upper end thin; see note for measured tissue diameters · source
The low end is not a macrophage diameter. Nibbering 1990 measured human blood monocytes at 421 fL in suspension, which is a sphere of 9.3 um, so that end is a monocyte volume converted to a diameter and not a measured macrophage. The 30 um upper end rests on a review statement rather than a measurement and is thin. The only measured human tissue macrophage diameters available are 14.2 um (carbon-negative) and 16.1 um (carbon-containing) in alveolar macrophages, from Baker J et al. 2025, ERJ Open Res (https://pubmed.ncbi.nlm.nih.gov/41189586/). Four cautions travel with those two numbers. The cohort is COPD patients and smokers and the same paper states COPD alveolar macrophages are larger than those of nonsmokers, so a healthy value would be lower. They are profile diameters measured on 4 um paraffin sections with no stereological correction stated, and a section through a cell is smaller than the cell unless it passes through the centre, so they underestimate. Those two errors run in opposite directions and neither is quantified here. And they sit below the 20 um threshold at which Szkalisity A et al. 2025, EMBO J (https://pubmed.ncbi.nlm.nih.gov/40195500/) excluded cultured human monocyte-derived macrophages as not yet differentiated, which is the evidence that a culture population and a tissue population are not the same cell and that the culture threshold must not be used as a floor for tissue. That paper is CC BY-NC: the licence restricts reuse of its figures, not citation of its numbers. EMPIAR-13420 segmentation will replace this whole row with a measured distribution.