Human glomerular mesangial cells express CD16 and may be stimulated via this receptor. CD16, a low affinity receptor for IgG, was found on cultured human glomerular mesangial cells (GMC) by Western blot analysis, cell ELISA and in situ hybridization. To characterize the molecule in more detail, reverse polymerase chain reaction was performed and the PCR products were analyzed. From sequence analysis and from hybridization experiments with oligonucleotides specific for either the transmembrane form or the glycosylphosphatidylinositol anchored form it was found that GMC-CD16 was similar to NK-CD16. This indicates that GMC express the transmembrane form of CD16. Comparison between nonstimulated GMC and GMC stimulated by aggregated gammaglobulin revealed no qualitative or quantitative difference in the expression of CD16. Incubation of GMC with aggregated gammaglobulin or with monoclonal antibodies to CD16 was followed by a time and dose dependent release of interleukin-6, suggesting that signals were transmitted by CD16. The occupancy of CD16 by immune complexes that may be deposited in various forms of glomerulonephritis might contribute to the perpetuation of inflammatory processes in the kidney.