Clinical, immunophenotypic and functional characterisation of T-cell leukaemia in six horses.
Authors: Rendle D I, Durham A E, Thompson J C, Archer J, Mitchell M, Saunders K, Millere J, Paillot R, Smith K C, Kydd J H
Journal: Equine veterinary journal
Summary
# T-cell Leukaemia in Horses: Clinical and Immunological Characterisation Lymphoid leukaemia remains exceptionally uncommon in equine practice, yet establishing robust classification methods—as routinely done in human oncology—could substantially improve diagnostic accuracy and guide targeted treatment protocols. Researchers examined six horses with T-cell leukaemia using clinical assessment, immunohistochemistry, flow cytometry analysis of peripheral blood mononuclear cells, and functional testing with mitogens to characterise the immunophenotypic profile and biological behaviour of their neoplastic lymphocytes. All six horses presented with circulating neoplastic lymphocytes in peripheral blood, with post-mortem examination of four cases confirming tissue invasion; immunophenotyping revealed a predominance of CD3+ T-cells in lymphoid tissues and notably a CD4+ subset in circulating peripheral blood, though clinical presentation and disease progression varied considerably across cases. Crucially, neoplastic lymphocytes harvested from four horses demonstrated a striking failure to proliferate when exposed to mitogenic stimulation, suggesting functional impairment distinct from normal T-cell activation patterns. Whilst this small case series provides a valuable foundation for understanding equine T-cell leukaemia's immunological signature, practitioners should recognise the marked variability in clinical course and recognise that flow cytometric phenotyping and functional assessment may be necessary to differentiate T-cell leukaemia from reactive lymphocytosis or other lymphoproliferative disorders in suspected cases.
Read the full abstract on PubMed
Practical Takeaways
- •T-cell leukaemia is rare in horses but should be considered in cases with unexplained lymphocytosis and variable clinical presentations; flow cytometry immunophenotyping can help confirm diagnosis
- •Detection of neoplastic cells in peripheral blood samples is a useful diagnostic marker, as all six cases showed circulating abnormal lymphocytes
- •This detailed characterisation provides a foundation for developing species-specific treatment protocols similar to those used in human haematology
Key Findings
- •Six horses with T-cell leukaemia presented with variable clinical signs and courses, with neoplastic lymphocytes detected in peripheral blood in all cases
- •Immunophenotyping revealed predominance of CD3+ T-cells in lymphoid tissues and CD4+ T-cells in circulating peripheral blood mononuclear cells
- •Neoplastic lymphocytes from 4 tested cases failed to proliferate in response to mitogen stimulation, suggesting impaired functional capacity
- •Post-mortem examination confirmed tissue invasion in 4 of 6 cases, establishing systemic disease