CD3+ and BLA.36+ cells do not occur in the epidermis and adnexal epithelia of normal equine skin.
Authors: Tranchina M M, Scott D W, McDonough S P
Journal: Equine veterinary journal
Summary
# Editorial Summary Unlike humans and mice, horses do not maintain a resident population of T lymphocytes within the epidermis and hair follicle epithelia of healthy skin. Tranchina, Scott and McDonough examined skin biopsies from 27 clinically normal horses using standard histology and immunohistochemical staining for CD3+ T cells and BLA.36+ B cells, finding no lymphocytic infiltration in either the epidermis or adnexal structures across any sample. This fundamental difference in normal cutaneous immunology has important diagnostic implications: whereas isolated lymphocytes in the epidermis might be considered a physiological finding in human or rodent dermatology, their presence in equine skin should prompt investigation for underlying pathology such as allergic dermatitis, infection, or other inflammatory conditions. Clinicians and pathologists interpreting equine skin biopsies can therefore treat any epidermal or follicular lymphocytic infiltration as abnormal, strengthening the diagnostic utility of histopathology in equine dermatological cases. This finding underscores the necessity of understanding species-specific skin immunology when evaluating biopsy specimens and designing appropriate treatment protocols.
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Practical Takeaways
- •Finding lymphocytes in equine skin biopsies is abnormal and warrants investigation for underlying skin disease or immune-mediated conditions
- •This baseline data helps veterinarians interpret histopathology results—lymphocyte infiltration in epidermis/adnexa is a significant diagnostic finding in horses
- •Normal equine skin differs from human and rodent skin in lacking resident epidermal T-cell populations, important for understanding species-specific skin immune responses
Key Findings
- •CD3+ T lymphocytes and BLA.36+ cells were not detected in epidermis or adnexal epithelia of any of 27 normal horse skin samples
- •Resident epidermal lymphocytes appear to be absent in normal equine skin, contrasting with healthy human and murine skin
- •The presence of lymphocytes in epidermis or adnexal structures should be considered abnormal in horses and may indicate pathology