Intrinsic factor of Castle is secreted by?

Intrinsic factor, a mucoprotein secreted by the parietal cells, binds with vitamin B12 of dietary origin and greatly enhances absorption of the vitamin. Absorption occurs by an active process in the terminal ileum. Intrinsic factor secretion is enhanced by stimuli that evoke H+ output from parietal cells. Pernicious anemia is characterized by atrophy of the parietal cell mucosa, deficiency in intrinsic factor, and anemia. Subclinical deficiencies in vitamin B12 have been described after operations that reduce gastric acid secretion, and abnormal Schilling tests in these patients can be corrected by the administration of intrinsic factor. Ref: Dohey G.M., Way L.W. (2010). Chapter 23. Stomach & Duodenum. In G.M. Dohey (Ed), CURRENT Diagnosis & Treatment: Surgery, 13e.