But in rheumatoid arthritis, that protein is missing in some immune cells.

VOA: special.2010.03.16

And how the cells shutdown is they actually die Harris Perlman says a protein in healthy immune cells causes them to die after they attack an invading virus or bacteria.

VOA: special.2010.03.16

The count measures immune cells that are killed off by the AIDS virus,HIV.

VOA: standard.2010.07.21

The immune system loses its ability to tell the difference between foreign materials and its own cells.

VOA: special.2010.06.15

She says the chimpanzee tissue showed a severe loss of immune system cells.

VOA: special.2009.09.08