both in vivo and in vitro , mice homozygous for the viable motheaten mutation show severe immunodeficiency , polyclonal b-cell activation and ig secretion , and spontaneous production of a lymphokine [ b-cell maturation factor ( bmf ) ] that directly drives the maturation of normal or tumor b cells to the state of active ig secretion .
C0021051
immunodeficiency
C0021027
ig