Search

A new cell line has been produced by fusing human cervical keratinocytes with HeLa cells. This cell line secretes eosinophil-activating activity upon stimulation with tumour necrosis factor (TNF). About one-third of the eosinophil-activating activity co-purifies with eosinophil-activating factor (EAF) from mononuclear cell supernatants. The purification procedure indicates that it resembles EAF in molecular weight and acidity. It also resembles EAF in its effect on eosinophils. Not only does it enhance the cytotoxic activity of eosinophils to antibody-coated schistosomula of Schistosoma mansoni, but it also increases the oxidative activity of eosinophils, as measured by reduction of nitroblue tetrazolium, and changes the morphology of eosinophils, affecting the distribution of F-actin in the cell.

Antibody-dependent cell-mediated cytotoxicity (ADCC) of infectious bovine rhinotracheitis (IBR)-infected bovine kidney cells (MDBK) by neutrophils was demonstrated. Neutrophils from bovine and sheep mammary exudate and peripheral blood, and also from human peripheral blood, were all active in the presence of anti-IBR antibody. The component of the ruminant neutrophil granules which was responsible for cytotoxicity appeared to be cationic protein since purified cationic protein lysed the virus-infected cells and heparin inhibited cytotoxicity. Human neutrophil cytotoxicity to herpes simplex virus (HSV)-infected human Chang liver cells was also inhibited by heparin. Human neutrophil cytotoxicity to IBR-infected bovine kidney cells did not appear to be mediated by cationic protein since it was inhibited by the chelators of oxidative intermediates DMSO, thiourea, tryptophane, benzoate and mannitol, and not by heparin.

To distinguish between direct and indirect involvement of oxygen metabolites in CTL cytotoxicity a comparison was made of cloned CTLs and mixed cells from mouse spleen. Tumour cells could be protected from cloned CTLs and from spleen CTLs by the thiol protecting reducing agents DTT and DETC. Cytotoxic activity was inhibited by diversion of reducing power from NAD(P)H to artificial electron acceptors and by the inhibitor of NAD(P) linked enzymes cibacron blue. Although H2O2 formation could be detected during the lysis of P815 by spleen CTLs it did not prove to be a necessary requirement for cytolysis since it was not formed when glutaraldehyde-treated P815 cells were lysed. Of the scavengers of toxic oxygen metabolites tested only the hydroxyl radical scavenger sodium benzoate inhibited cytotoxicity.