Sun 10 Oct, 2010 08:44 pm
Memory B cells are essential for the long-lived immunity that arises after immunisation. To develop into memory cells, B cells have to survive the natural process of apoptosis, or programmed cell death, that occurs following a large immune response.
that means which
or leave out that and use occurring
Or leave it as it is. It's perfectly comprehensible to any English-speaker.