Evaluation of IgG concentration and IgG subisotypes in foals with complete or partial failure of passive transfer after administration of intravenous serum or plasma.
Authors: McClure J T, DeLuca J L, Lunn D P, Miller J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Passive Transfer Treatment with Intravenous Products Foals with failure of passive transfer (FPT) face significant health risks, yet optimal treatment protocols remain unclear. McClure and colleagues compared the effectiveness of intravenous equine plasma and concentrated serum products in 46 affected foals, measuring total IgG concentration and specific antibody responses (against equine influenza and tetanus toxoid) over three days post-transfusion. Plasma proved more efficient on a per-unit basis, delivering approximately twice the IgG concentration per volume, though the serum product required double the units to achieve comparable serum IgG levels—suggesting that 1 unit of plasma is roughly equivalent to 2–3 units of concentrated serum. Body weight, baseline IgG, foaling season, and product type all influenced post-transfusion outcomes, whilst the quality of antibody transfer (measured by IgGa, IgGb, and IgG(T) subisotypes) was equivalent gram-for-gram between products. For practitioners managing FPT, these findings provide evidence-based dosing guidance and confirm that both products are viable options; choice between them may be determined by availability, cost, and practical handling rather than immunological efficacy.
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Practical Takeaways
- •When treating FPT in foals, plasma is more efficient per unit volume than concentrated serum (1 unit plasma ≈ 2-3 units serum), but either product can achieve equivalent IgG levels with appropriate dosing adjustments
- •Consider foal body weight and pretransfusion IgG concentration when determining dosage, as these factors significantly influence treatment outcomes
- •Both products deliver functionally equivalent antibody responses when normalized for total IgG content, so product choice can be based on practical availability and cost considerations
Key Findings
- •Plasma treatment achieved greater increases in post-transfusion serum IgG concentrations compared to concentrated serum product, primarily because plasma contained approximately twice the IgG per unit
- •Similar foal serum IgG concentrations can be achieved 3 days post-transfusion by administering 1 unit of plasma or 2-3 units of serum product
- •Body weight, pretransfusion IgG concentration, number of product units transfused, foaling season, and product type significantly affected post-transfusion IgG levels
- •Antigen-specific IgG subisotype changes were similar between plasma and serum treatments when adjusted for the total amount of IgG transfused