Solid-phase immunoassay for the vitamin B 12-binding protein transcobalamin II in human serum

• Published in: Analytical biochemistry Vol. 124; no. 1; pp. 92 - 101
• Main Authors: Frater-Schroder, Marijke, Kierat, Lucja, Andres, Roger Y., Römer, Jürg
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1982
• ISSN: 0003-2697; 1096-0309
• DOI: 10.1016/0003-2697(82)90225-1

A solid-phase radio immunoassay was developed for total immunoreactive transcobalamin II (TC II). Rabbit antihuman TC II antiserum (which recognizes both apo- and holo-TC II), was immobilized by covalent binding to acrylamide-acrylic acid copolymer beads. A normal mean and SD for immunoreactive TC II in serum was determined in 130 healthy adult individuals and found to be 1150 ± 250 ng/liter cobalamin equivalent. Mean holo-TC II ( N = 30), estimated by substraction of apo-TC II from total TC II, was 137 ng/liter bound cobalamin (or 12% of total TC II). Three patients with lack of functional TC II had immunoreactive TC II levels between 22 and 39% of normal mean, which demonstrated that the solid-phase bound antiserum recognized deficient TC II molecules, whereas the same antiserum in its soluble form did not. Eight out of nine individuals, recognized as heterozygous for TC II deficiency, had TC II levels below the normal range, on the order of 50% of the normal mean. The stability of immunoreactive TC II was strongly enhanced by the presence of an unknown serum factor not corresponding to serum albumin.