Panton-Valentine toxin. Electron density map graphic of the molecular structure of a sub-unit of the Panton- Valentine leucocidin (PVL) toxin from the bacteria Staphylococcus aureus. This is the F sub-unit, it combines with a S sub-unit to form the toxin. The toxin targets white blood cells, part of the body's immune system. It makes pores in the white blood cell's membrane, causing the cell contents to leak, and thus killing the cell. This destruction of cells leads to skin and soft tissue infections. These are mainly abscesses, but it can also cause pneumonia. The toxin has been found in strains of the antibiotic-resistant MRSA (methicillin-resistant S. Aureus) bacteria.