Phenotype- and age-associated variations in non-specific agglutinins and complement components (C3 and C5a) in camels: Implications for transfusion compatibility and immune function.

Background and aim: Blood transfusion in camels is hindered by poorly understood blood group systems, non-specific agglutinins, and a lack of standardized cross-matching protocols. Non-specific agglutinins, primarily immunoglobulin M (IgM), can lead to cross-reactivity, while complement components C3 and C5a impact transfusion outcomes and immune responses. This study aimed to evaluate age- and phenotype-related variations in non-specific agglutinins, C3, and C5a in camels to assess implications for transfusion compatibility and innate immunity.

Materials and methods: A total of 360 healthy male camels representing three phenotypes (black, yellow, and white) and four age groups (3-5, 5-8, 8-10, and >10 years) were sampled from slaughterhouses in Saudi Arabia. Serum agglutinin titers were determined using hemagglutination assays with heterologous red blood cells (RBCs). Heat inactivation (56°C, 30 min) and sheep RBC (SRBC) adsorption were applied to assess antibody specificity. C3 and C5a concentrations were quantified using an enzyme-linked immunosorbent assay. Statistical analyses employed analysis of variance with Tukey's post hoc test (p<0.05).

Results: Yellow camels exhibited the highest agglutinin titers (up to 1338.4 ± 119.3 against black RBCs), with significant age-related increases. White camels showed the lowest reactivity but demonstrated marked age-related increase in C3 (3.252 ± 0.578 to 4.829 ± 0.983 μg/mL) and C5a (2.776-3.525 μg/mL). Black camels displayed moderate complement levels, peaking in older animals. Heat inactivation and SRBC adsorption substantially reduced titers across all phenotypes, confirming IgM dominance. Age-related increases in agglutinins and complement components indicated immune maturation or cumulative antigen exposure.

Conclusion: Phenotypic and age-related immune differences significantly affect transfusion compatibility in camels. Yellow camels' high agglutinin activity poses greater transfusion risks, whereas white camels' lower reactivity and higher complement activity suggest potential as universal donors. Age-adjusted and phenotype-matched transfusion protocols, pre-transfusion heat inactivation, and monitoring C5a in older camels could enhance transfusion safety. This is the first comprehensive study linking camel phenotype and age to complement activation (C3 and C5a), providing a framework for improved transfusion practices and future genomic research into complement-related traits.