B cells become memory B cells or plasma cells that produce antibodies after affinity maturation with T cells.

“once the antibodies the b-cells are we call it affinity matured that is they get better and better at binding to the piece of virus that they attach to and this occurs in the lymph nodes where the architecture is very important because we've got t-cells that are absolutely necessary to help them develop in those lymph nodes but then they exit the lymph nodes about 7 to 14 days later and then they become either memory B cells which are very small B cells that circulate or they go into the bone marrow where they become these big plasma cells which essentially become the factories of antibodies”