Morphology of synovial cells of the human in organ and explant cultures

: Biopsy material of synovial tissue was taken from 36 patients (with arthrosis, rheumatoid arthritis, traumatic and unaffected joints). Cell and tissue cultures, as well as cells dissociated by enzymes, were investigated by light microscopy (LM), immunohistochemistry, and electron microscopy. Synovial A-cells were endowed with all morphological characteristics of phagocytic capacity but lacking the peroxidase reaction. In contrast to the monocytes, they were not immunostained by OKM-1 antibodies. The A-cells could be observed in subsequent in vitro growth for up to 2 weeks. In addition to B-cells, a third cell type was identified. This cell type had the morphological characteristics of a dendritic cell and was glass and plastic adherent. It can be referred to also as a stellate cell. We assume that these stellate cells represent modified synovial fibroblasts.