IgG antibody responses to an inhaled antigen in horses with “heaves” (recurrent airway obstruction).

The research paper seeks to analyze the immune response in horses experiencing recurrent airway obstruction, also known as “heaves,” when exposed to an inhaled antigen. The findings contradict popular belief, revealing that these horses demonstrate weaker IgG responses compared to healthy horses.

Research Methodology

• The scientists developed an experimental system to analyze pulmonary immune responses in horses affected by “heaves” in comparison to healthy ones.
• The hypothesized understanding was that the reaction to an inhaled antigen in affected horses would vary from healthy ones and chronic pulmonary inflammation could affect the production of IgG isotypes.
• Different horses were kept in the same conditions (stabled, fed dusty hay) and exposed to an inhaled solution of keyhole limpet hemocyanin (KLH), a commonly used antigen.
• Prior to and following this exposure, serum and bronchoalveolar lavage fluids (BALFs) were collected from the horses.
• Differential cell counts were conducted on the cells in the BALF.
• Concentrations of IgGa, IgGb, IgG(T), and combined IgG specific for KLH in the BALF and sera were noted using an enzyme-linked immunosorbent assay (ELISA).

Findings

• The percentage of neutrophils in the BALF of affected horses increased 4-6-fold over healthy horses.
• Compared to diseased horses, combined IgG specific for KLH was significantly higher in BALF and serum of healthy horses.
• Differences in IgG isotypes were also noted. In the BALF of diseased vs. healthy horses, only IgGb specific for KLH increased noticeably.

Interpretation of Findings

• The differences observed could be due to increased destruction of the antigen before it could interact with lymphocytes, down-regulation of IgGb production due to inhibitory cytokines in diseased horses, or the binding of IgGb to Fc receptors on abundant neutrophils in the lungs of sick horses.
• The research contradicted the popular belief by suggesting that horses with heaves have weaker immune responses when exposed to an aerosolized protein, leading to lower IgG responses compared to healthy horses.