Identification of a highly mobilizable subset of human neutrophil intracellular vesicles that contains tetranectin and latent alkaline phosphatase

Tetranectin, a protein recently identified in a wide variety of human secretory cells (Christensen, L., and I. Clemmensen. 1989. Histochemistry. 92:29-35) was found to colocalize with latent alkaline phosphatase activity in fractions well separated from azurophil granules, specific granules, gelatinase-contain-ing granules, and plasma membranes when postnuclear super-natants of nitrogen-cavitated neutrophils were fractionated on discontinuous Percoll density gradients. Stimulation of intact neutrophils with nanomolar concen-trations of FMLP, leukotriene B4, 10-100 U/ml of tumor ne-crosis factor, and granulocyte-macrophage colony-stimulating factor resulted in parallel release of tetranectin and transloca-tion of alkaline phosphatase to the plasma membrane. Fur-thermore, intracellular pools of tetranectin and latent alkaline phosphatase were completely released from neutrophils under conditions that barely induced release of specific granules con-taining B12-binding protein. These findings indicate that tetra-nectin and latent alkaline phosphatase define an easily mobil-izable population of cytoplasmic storage organelles in human neutrophils which are functionally distinguishable from azuro-phil, specific, and gelatinase-containing granules. These or-ganelles may play an important role as stores of membrane proteins that are mobilized to the cell surface during stimula-tion by inflammatory mediators. (J. Clin. Invest. 1990. 85:408-416.) exocytosis * gelatinase * intracellular membranes * subcellular fractionatio