Histamine-induced adherence and migration of equine eosinophils.

This research study explores the effects of histamine on the adherence and migration of eosinophils – a type of white blood cell – in horses. The paper also looks at how different types of histamine receptors and cell surface adhesion molecules are involved in this response.

Research Methodology

• The study used 8 healthy ponies for the experiments. They primarily looked at how histamine affected eosinophil adherence to serum- or fibronectin-coated plastic and also migration in a microchemotaxis assay.
• Sometime, prior to the experimentation, eosinophils were pretreated with histamine receptor antagonists or monoclonal antibodies raised against cell adhesion molecules.
• They compared the effects of histamine on equine neutrophil adherence and migration, to see if the effects were specific to eosinophils or not.

Findings and Results

• The researchers found that histamine resulted in the adherence of equine eosinophils, but not neutrophils, to serum and fibronectin-coated plastic.
• They also found that histamine caused the migration of equine eosinophils, but again, not neutrophils.
• The actions of histamine on the adherence and migration of equine eosinophils could be blocked by the use of histamine receptor antagonists chlorpheniramine and mepyramine, but not by other histamine receptor antagonists such as cimetidine and thioperamide.
• The results also showed that monoclonal antibodies against CD18, a type of protein found on the surface of some cells, could reduce histamine-induced equine eosinophil adherence to serum- and fibronectin-coated plastic.

Conclusions and Implications

• The researchers concluded that histamine, when released from mast cells or basophils – two other types of white blood cells – could stimulate the adherence and migration of equine eosinophils. This effect appears to be mediated via the activation of H1 histamine receptors and CD18.
• This implies that histamine may play a role in regulating how equine eosinophils behave particularly their function in combating parasitic infections or in responses to allergens – specifically in horses with insect hypersensitivity.

The researchers suggest further studies to explore the potential therapeutic applications of these findings in managing parasitic infections and allergies in horses.