Complex sentence: When exposed to infected/dysfunctional somatic cells, T C cells release the cytotoxins perforin and granulysin, which form pores in the target cell's plasma membrane; this causes ions and water to flow into the target cell, making it expand and eventually lyse.
Split into simpler sentences: When exposed to infected/disfunctional somatic cells, T C cells release the cytotoxins perforin and granulysin. These form pores in the target cell's plasma membrane causing ions and water to flow into the target cell that make the cell expand and eventually lyse.