Effects of allergen-specific immunotherapy on peripheral blood regulatory T cells and serum concentrations of cytokines and immunoglobulins in horses with allergic dermatitis.

The research aimed to assess how allergen-specific immunotherapy (ASIT) impacts T cells, cytokines, and immunoglobulins in horses suffering from allergic dermatitis. It was found that while the therapy resulted in minor changes, it was not significant enough to trigger crucial shifts needed, such as T cell tolerance and the production of protective Th1 cells.

Participants and Method

A total of 32 horses with allergic dermatitis undergoing ASIT treatment and 10 healthy horses were involved in the research. Their peripheral blood regulatory T cells (Treg) and serum levels of various cytokines and immunoglobulins were monitored periodically over year.

• Blood samples from these horses were collected at baseline, and then after every 3 months up to a total of 12 months. The aim was to observe any physiological changes following ASIT treatment.
• Another aim was to monitor the evolution of Treg cell population in peripheral blood and serum level changes in cytokines and immunoglobulins.

Findings and Interpretation

Despite more than half of the horse owners reporting clinical improvement in their horses, no significant impact of ASIT was visible on the horses’ immune responses.

• No effect on CD4CD25 Treg cells was observed during the one year treatment period.
• There was no significant difference in the percentage of CD4 T cells between ASIT-treated horses and control horses, hinting that the treatment does not impact CD4 T cell count.
• The count of CD25 T cells was persistently higher in ASIT-treated horses as compared to the control group.
• ASIT treatment did not alter serum levels of certain cytokines like TGF-β, IL-10, and IFN-γ which are critical for immune response.
• No alterations in serum concentrations of immunoglobulins IgA and IgG4 were observed. However, a temporary reduction in total IgE levels was noticed in the treatment group, but the levels rose again at the end of the study.

Conclusions and Further Studies

The study concluded that ASIT treatment for allergic dermatitis in horses were insufficient to induce significant changes in immune responses. Treatment did not lead to T cell tolerance or catalyse a shift in cytokine production to the more protective Th1 cells.

• This highlights the need for further research in this area, with possible experiments with new vaccine compositions and administration protocols.
• The treatment while appreciated by the horse owners in more than half of the cases, may not have had a significant biological impact, and further studies may elucidate the reasons why.