Indirect immunofluorescence staining of contractile proteins in smeared cells by smooth muscle antibodies. The influence of chelating agents

A lymphoblastoid cell line of human origin (`Moore') showed short or long microvilli when stained in a smeared state by indirect immunofluorescence using human serum containing smooth muscle antibodies (SMA), horse anti-lymphocyte immunoglobulin (ALI) or rabbit anti-species serum. A prerequisite for obtaining a positive reaction with SMA-positive serum was that a chelating agent was present in the suspending medium when preparing the smears. ALI and anti-species serum, however, stained the microvilli in the presence of calcium. These sera also stained live suspended lymphoblastoid cells, which SMA did not. The brush-border of monkey duodenal epithelial cells showed the same prerequisites for staining with SMA as the lymphoblastoid cells.