Intracellular localization of the migration inhibitory factor (MIF) in a long-term human lymphoid cell line

Subcellular fractions of the human lymphoid cell line PGLC-33H were obtained by N2 cavitation and differential centrifugation. The purity of the fractions was assessed by the use of the following marker enzymes: beta-glucuronidase for the lysosomal-intermediate fraction; a nonspecific esterase for the microsomal fraction; and LDH for the supernatant fraction. These subcellular fractions were studied for MIF activity utilizing human lymphoid cells from established lines as target cells. MIF activity was most consistently found in the microsomal fraction. Also, MIF activity was closely associated with the relative specific activity of exterase. No such correlation with MIF activity could be demonstrated for beta-glucuronidase or LDH.