Fine structural analysis of rabbit synovial cells. II. Fine structure and rosette-forming cells of explant and monolayer cultures.

The fine structure and plasma membrane receptors of explant and monolayer cells of normal rabbit synovium were studied. In explants about 10% of the cells were round and formed rosettes with IgC and C3 markers, whereas the remaining cells were stellate, resembled young fibroblasts, and had no receptors for IgG and complement. Monolayer cells looked like fibroblasts, produced fine extracellular fibrils and hyaluronate, and formed no rosettes. Thus early cultures contain both macrophages and fibroblasts but only the latter persist in monolayer.