lymphoblast studies - (Sep/14/2009 )

I am new to the field of cell culture and am working on lymphoblast studies. Does any one here work with these cells. When i initially grow them they are clumps but later on they form a sediment that is not clumps any more, please can any one help me? I will have a couple more questions if any one works on these cells. thanks in advance

T or B cells? Human or mouse? What stimulation?
At what point are the cells clumping and at what point (day are they sedimenting)?
When no longer clumpy, are the cells alive or dead?

They are human cells and they clump after 4-5 passages. The viability of the cells is decreased for about 10- 15% but they are still viable.

How are you stimulating them? I tend to think of these cells in terms of days past stimulation. How many days past stimualtion is 4 passages?

i grow the cells till they are around 2 million/ ml and then they undergo BPA treatment of various concentration