title: Autoantibodies to lactate dehydrogenase in serum identified by use of immobilized protein G and immobilized jacalin, a jackfruit lectin.
abstract: In this method for identifying autoantibodies to lactate dehydrogenase (anti-LDs) in serum, we used immobilized Protein G to bind IgG-complexed LD and immobilized jacalin to bind IgA-complexed LD, leaving non-complexed LD in solution. The non-complexed LD and total LD were kinetically measured. We report results as LD bound to immobilized Protein G and LD bound to immobilized jacalin. Using sera demonstrating IgG and IgA anti-LDs by immunoelectrophoresis (IEP), respectively, we optimized the method for incubation time and concentration of binding agents. We demonstrated concomitant binding of LD and greater than or equal to 98% of IgG and of LD and greater than or equal to 92% of IgA. For LD bound to immunobilized Protein G the detection limit was 10 U/L, within- and between-run CVs ranged from 2.9% to 9.1%, and values for normal sera were less than or equal to 3% of total LD. Results for LD bound to immobilized jacalin were similar. We tested 10 sera displaying aberrant LD electrophoretograms: In seven, LD bound to immobilized Protein G was increased (range: 26-99% of total LD), indicating IgG-complexed LD. This was confirmed by IEP, demonstrating IgG1,2, or IgG3 anti-LDs in these sera. In the other three sera, LD bound to immobilized jacalin was increased (range: 38-72% of total LD), indicating IgA-complexed LD. This was confirmed by IEP, demonstrating IgA anti-LDs in these sera. Evidently this method is an alternative to IEP for identifying anti-LDs in serum.
authors.affiliation: Department of Clinical Chemistry, Het Diaconessenhuis, Leiden, The Netherlands.
authors.forename: E T
authors.initials: ET
authors.lastname: Backer
authors.forename: G A
authors.initials: GA
authors.lastname: Harff
mesh_terms: D001323:Autoantibodies / Q000032:analysis*; D004586:Electrophoresis; D006801:Humans; D007122:Immunoelectrophoresis; D007070:Immunoglobulin A / Q000032:analysis; D007074:Immunoglobulin G / Q000032:analysis; D007770:L-Lactate Dehydrogenase / Q000276:immunology* / Q000378:metabolism; D037102:Lectins; D009419:Nerve Tissue Proteins; D037121:Plant Lectins; D011786:Quality Control
chemical_list: D001323:Autoantibodies; C029152:G-substrate; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D037102:Lectins; D009419:Nerve Tissue Proteins; D037121:Plant Lectins; C043696:jacalin; D007770:L-Lactate Dehydrogenase