Overexpression of B-cell specific activator protein(BSAP/Pax-5)in a late B cell is sufficient to suppress defferentiation to an immunoglobulin high producer cell with plasma cell phenotype(B細胞特異的転写因子(BSAP/Pax-5)の過剰発現は、後期B細胞株において形質細胞の表現型をもつ高免疫グロブリン産性細胞への分化を抑制する)