title: Effects of papain on the agglutination of canine red cells with serum autoantibodies.
abstract: The papain test, which detects incomplete anti-red blood cell (RBC) autoantibodies in serum, was positive in 12 out of 16 anaemic dogs. Positive results were significantly correlated (chi 2 = 11.1, P < 0.001) with increased levels of RBC-bound immunoglobulin, but in three of these cases it was considered that a diagnosis of autoimmune haemolytic anaemia could not be justified. Furthermore, enzyme-linked antiglobulin test measurements of RBC-reactive serum IgG were increased in only three of the dogs with a positive papain test. Papainised canine RBC did not consistently take up more serum IgG than untreated cells in an indirect enzyme-linked antiglobulin test. However, the zeta potential of the RBC was reduced after enzyme treatment, and electrophoretic analysis revealed that glycophorins, which bear a strong negative charge, were cleaved from the cell membrane. It is concluded that a positive papain test alone is not reliable in the diagnosis of canine autoimmune haemolytic anaemia and that the enzyme increases the agglutinability of RBC by reducing the mutually repulsive electrostatic forces between the cells, rather than by increasing the amount of autoantibody bound.
authors.affiliation: Department of Pathology and Microbiology, Medical School, University of Bristol.
authors.forename: R N
authors.initials: RN
authors.lastname: Barker
authors.forename: D R
authors.initials: DR
authors.lastname: Jones
mesh_terms: D000740:Anemia / Q000097:blood / Q000662:veterinary*; D000818:Animals; D001323:Autoantibodies / Q000032:analysis / Q000097:blood*; D004283:Dog Diseases / Q000097:blood*; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D004910:Erythrocyte Membrane / Q000737:chemistry / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects / Q000502:physiology*; D006384:Hemagglutination / Q000187:drug effects*; D008565:Membrane Proteins / Q000097:blood / Q000302:isolation & purification; D008970:Molecular Weight; D010206:Papain / Q000494:pharmacology*
chemical_list: D001323:Autoantibodies; D008565:Membrane Proteins; D010206:Papain