Prolonged growth of activated B lymphocytes requires interaction with helper T cells

Resting B lymphocytes acquire upon activation responsiveness to soluble factors that support their growth and differentiation. We have studied the growth requirements of anti-mu pre-activated B lymphocytes in vitro. We found that activated B lymphocytes did respond to soluble factors from helper T cells by entering the cell cycle but cell-cell contact with specific helper T cells was required for prolonged growth of activated B lymphocytes. Thus, activated B lymphocytes must receive activation signals from helper T cells in order to stay in the proliferative phase of the cell cycle.