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&#x2009;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&#x2009;=&#x2009;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&#x2009;6-positive. Agreement analyses were supportive of FEA&#x2009;6 being distinct from FEAs&#x2009;1-5. NOAb were detected in 11 cats (5.7%), none of which were anti-FEA 6. Only FEA&#x2009;1-negative status was significantly associated with the presence of NOAb (OR&#x2009;=&#x2009;6.6, 95% CI, 1.9-23.1; p&#x2009;<&#x2009;0.001). Significant associations were observed between the expressions of FEAs 1 and 4 (&#x3c7;&#x2009;=&#x2009;25.7, p&#x2009;<&#x2009;0.001), and FEAs 3 and 5 (Fisher's exact test, p&#x2009;<&#x2009;0.001), respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: The immunogenicity and prevalence of the newly discovered FEA&#x2009;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.