RED CELL-REACTIVE NONSPECIFIC IMMUNOGLOBULINS AND AUTOANTIBODIES IN THE SERA OF NORMAL AND ANEMIC DOGS

The levels of red blood cell (RBC) membrane-reactive IgG were measured in sera from normal and anaemic dogs using an enzyme-linked immunosor bent assay with erythrocyte ghosts as the target antigen (g-ELISA). Th e anaemic dogs were classified as cases of primary autoimmune haemolyt ic anaemia (AIHA), other anaemias with elevated levels of RBC-bound im munoglobulin detected by a direct enzyme-linked antiglobulin test (DEL AT), or DELAT-negative anaemias. The g-ELISA detected IgG capable of b inding RBC membranes in all the serum samples tested, and the levels w ere significantly higher (P<0.05) in dogs with AIHA than in cases of D ELAT-negative anaemia or in healthy animals. When sera were preabsorbe d with RBC ghosts, g-ELISA readings were reduced in two of three AIHA cases that were tested, but not in dogs from any other group. There wa s no correlation between g-ELISA results and serum IgG levels in the c ases of AIHA, but there was a significant relationship (r(s)=0.74, P<0 .001) between these parameters in the dogs with other DELAT-positive a naemias. When spectrin(s) from the internal RBC membrane skeleton was used as the target antigen in the s-ELISA, sera from all groups of ana emic dogs yielded a wide range of values. Although the levels of spect rin-reactive IgG were significantly higher (P<0.05) in AIHA cases than normal dogs, suggesting that haemolysis provoked production of anti-m embrane skeleton antibodies, the highest reading was recorded in a hea lthy animal. It is concluded that all canine sera contain IgG non-spec ifically reactive with RBC membranes and that serum antibodies against the erythrocyte surface can also be detected in some dogs with primar y AIHA. Distinct spectrin-reactive serum IgG antibodies can also be de monstrated in normal and AIHA positive dogs.