Red cell-bound immunoglobulins and complement measured by an enzyme-linked antiglobulin test in dogs with autoimmune haemolysis or other anaemias

Abstract

A direct enzyme-linked antiglobulin test ( DELAT) was used to measure IgG, IgM, IgA and C 3 bound to the red blood cells ( RBC) of anaemic dogs. One or more of these parameters was raised in 78 per cent of the cases tested, and elevated levels of bound IgG, IgM, IgA and C 3 was the most common pattern recorded. When the DELAT-positive animals were divided into two groups on the basis of clinical findings, the two categories differed serologically. Cases diagnosed clinically as primary autoimmune haemolytic anaemia ( AIHA) were typified by the demonstration of specific antibody binding to RBC, had significantly higher levels of RBC-bound IgG (P<0·001) and IgM (P<0·02) and included a significantly (P<0·01) higher proportion of the dogs with at least three DELAT parameters raised. The second group comprised the DELAT-positive dogs with other diseases. In most of these cases, RBC-specific antibody was not detectable and there was a significant (r s=0·62, P<0·001) relationship between RBC-bound and serum IgG levels, suggesting that the immunoglobulin was reacting with the RBC non-specifically in a concentration-dependent manner. It is concluded that elevated levels of RBC-bound immunoglobulin and, or, complement are detectable with the DELAT in most anaemic dogs, but that this finding is not necessarily associated with autoimmune haemolysis.