Characterization of post-transfusion anti-FEA 1 alloantibodies in transfusion-naive FEA 1-negative cats

Abstract

Objectives: The aim of this study was to characterize anti-feline erythrocyte antigen (FEA) 1 alloantibodies following sensitization of FEA 1-negative cats, including their rate of appearance, agglutination titer over time and immunoglobulin class. A secondary aim was to obtain polyclonal anti-FEA 1 alloantibodies to increase the availability of FEA 1 blood typing. We also describe a case study documenting an acute hemolytic transfusion reaction in a transfusion-naive FEA 1-negative feline patient that received FEA 1-positive blood.

Methods: In this prospective clinical study, 35 cats with blood group type A underwent extensive blood typing for FEA 1-5. Two cats were identified as FEA 1-negative; these cats were transfused uneventfully with 50 ml of FEA 1-positive, but otherwise compatible, packed red blood cells. Post-transfusion blood samples were collected routinely as long as anti-FEA 1 alloantibodies were detected. Appearance of anti-FEA 1 alloantibodies was detected using a gel column crossmatch method.

Results: Anti-FEA 1 alloantibodies were detected as early as 5 days post-transfusion and remained detectable for over 400 days in one cat. Agglutination titers in both cats were relatively weak (1:1 to 1:8). The main immunoglobulin class was IgM.

Conclusions and relevance: Transfusion of FEA 1-negative, transfusion-naive cats with FEA 1-positive blood results in production of post-transfusion anti-FEA 1 alloantibodies as early as 5 days post-transfusion. Our results confirm the potential immunogenicity of FEA 1 and support crossmatching prior to a blood transfusion, even in transfusion-naive cats. Further studies are needed to better document the clinical importance of these post-transfusion antibodies, as well as to facilitate routine blood typing for the FEA 1 antigen in cats.

Keywords: Feline erythrocyte antigen; Mik antigen; alloantibodies; crossmatch; transfusion.

Figure 1

(a) Crossmatches between feline erythrocyte antigen (FEA) 1-negative index cat 2 and its respective FEA 1-positive donor at days 2–7 post-transfusion. Index cat 2 developed anti-FEA 1 alloantibodies as early as day 5 post-transfusion. (b) Index cat 2’s anti-FEA 1 alloantibody agglutination titers at day 7 post-transfusion reaching a maximum of 1:32. Crossmatching was performed between index cat 2 and its respective FEA 1+ donor

Figure 2

Graph indicating the anti-feline erythrocyte antigen (FEA) 1 agglutination titers over time of index cats 1 and 2. Day 0 corresponds to the day of primotransfusion for both index cats 1 and 2. The arrows correspond to when index cat 1 received its second, third and fourth transfusions, administered 72, 232 and 334 days after initial transfusion, respectively

Figure 3

The case report index cat was crossmatch-compatible with three previously typed feline erythrocyte antigen (FEA) 1-negative cats and two FEA-1 positive cats. The index cat’s auto-control at the time of testing was negative