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

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.