Prevalence of a Novel Immunogenic Feline Erythrocyte Antigen (FEA 6) and Expression Patterns Between FEAs

Abstract

Background: After the identification of five novel feline erythrocyte antigens (FEAs) and evidence establishing FEA 1's immunogenicity, attempts to sensitize a cat to FEA 4 unexpectedly resulted in the production of alloantibodies directed against an unknown antigen, named FEA 6.

Objectives: To estimate the prevalence of FEA 6 as a presumably new antigen, identify corresponding naturally occurring alloantibodies (NOAb), and investigate the associations between known FEAs.

Animals: Two hundread and seven cats.

Methods: Prospective blood typing for FEAs 1-6 was conducted in Type A cats (n = 193), followed by serial crossmatching in groups of 3-7 cats to detect NOAb and identify their target FEA. Agreement between FEA 6 blood typing and other FEAs was assessed. Associations between FEAs were evaluated to identify expression patterns.

Results: Among 193 Type A cats, 67% were FEA 6-positive. Agreement analyses were supportive of FEA 6 being distinct from FEAs 1-5. NOAb were detected in 11 cats (5.7%), none of which were anti-FEA 6. Only FEA 1-negative status was significantly associated with the presence of NOAb (OR = 6.6, 95% CI, 1.9-23.1; p < 0.001). Significant associations were observed between the expressions of FEAs 1 and 4 (χ² = 25.7, p < 0.001), and FEAs 3 and 5 (Fisher's exact test, p < 0.001), respectively.

Conclusions and clinical importance: The immunogenicity and prevalence of the newly discovered FEA 6 raise concerns regarding its clinical relevance and role in posttransfusion sensitization. FEA 1/FEA 4 and FEA 3/FEA 5 pairs might belong to distinct antigenic systems.

Keywords: Mik antigen; alloimmunization; blood typing; crossmatch; naturally occurring alloantibodies; transfusion.