A defect of CD16-positive monocytes can occur without disease.

The CD16-positive monocytes have been first described in 1988 but to date no selective defect in the number of these cells in blood has been reported. We now describe a family in which three of four siblings lack both CD16-positive monocyte subsets, i.e. the nonclassical and the intermediate monocytes. All three had CD16-positive monocytes of 2 cells/μl or less as compared to 52±18 cells/μl in healthy controls. The index case was affected by recurrent pleural effusion and infections and had evidence of an auto-inflammatory condition but no mutation of any of the relevant candidate genes. The other two siblings without CD16-positive monocytes were apparently healthy. There was no defect in serum M-CSF levels and no mutation in the M-CSF and M-CSFR genes. The data indicate that the absence of CD16-positive monocytes in blood does not lead to disease.