Unusual selective immunoglobulin deficiency in an Arabian foal.

This research article discusses a rare case of selective immunoglobulin deficiency in a 10-month-old Arabian horse. The foal showed non-detectable levels of certain immunoglobulins (IgM, IgA, and IgG(T)), with only normal levels of IgG present. Despite an atypical response to the B-cell activator lipopolysaccharide (LPS), responses to T-cell activators were normal. Post-death examination revealed inflammation in various joints, organ atrophy and edema, lymphocyte depletion, and subacute inflammatory infiltrates in the kidney, synovium, liver, and brain. The cause of the deficiency remains unknown, and it represents a novel form of immunodeficiency in horses.

Immunoglobulin Deficiency in Arabian Foal

• The study was prompted by a suspected immunoglobulin (Ig) M deficiency in a 10-month-old Arabian foal. In the veterinary field, detection of such deficiencies in young animals can be crucial for effective treatment and survival.

Ig Levels in Foal

• The study revealed lowered to non-measurable concentrations of IgM, IgA, and IgG (T) — essential immunoglobulins that play a role in defending the body against infections. However, the foal had a normal concentration of IgG.

Blood Lymphocyte Blastogenesis Test

• On testing the foal’s blood lymphocytes for response to stimulators, a weak response was observed towards the B-cell mitogen, lipopolysaccharide (LPS). In contrast, the responses to T-cell mitogens were found to be normal. This suggests that the foal’s B cells were not responding normally and pointing towards a B-cell-related immunodeficiency.

Postmortem Examination Findings

• The post-mortem examination revealed inflammation in the left tibiotarsal and both scapulohumeral joints. Atrophy (shrinkage due to lack of use) and edema (swelling due to fluid accumulation) were seen in the foal’s lymph nodes.
• The thymus and spleen, two important organs in the immune system, showed signs of lymphocyte depletion, indicating a weakened immune arsenal.
• The examination also revealed a subacute inflammatory infiltrate in the kidney, synovium, liver, and brain. Despite these extensive signs of inflammation, no causative agents were identified, implying an underlying immune disorder rather than an external infection.

Conclusion

• The findings and outcomes of this case report outlined a unique form of immunodeficiency disease in an Arabian foal, not previously reported. This discovery broadens the range of potential immunologic disorders to consider in veterinary diagnoses and improves the understanding of equine immune function and potential genetic disorders.