The effects of tumor sera on cell shape and photosynthesis of Euglena gracilis.

Cells of Euglena gracilis treated with human sera show a marked change in cell shape: Fully elongated cells have nearly totally been transformed to disk-shaped cells. This serum-mediated contraction is followed by irreversible cytolysis. Disintegration of chloroplast membranes leads to decreased photosynthetic O2 evolution. Sera from humans suffering from tumors reveal higher lytic activities than sera from individuals not suffering from tumors. Heating sera at 56 degrees C for 10 min or addition of EDTA destroyed or inhibited, respectively, the lytic activities completely. Polysaccharides transformed in polyanions by sulphatisation like dextransulphates or heparin seem to protect Euglena against serum activities. The effects described for human sera are believed to display the role of the complement pathway in the cytolysis of Euglena gracilis.