Immunologic function in horses after non-specific immunostimulant administration.

This research aimed to understand the effects of administering inactivated Propionibacterium acnes, a biological response modifier, on the immune function of healthy young horses, with a focus on phagocytic activity, lymphocyte subpopulations, and lymphokine-activated killing cell response. The study found that the immunostimulant induced several immune changes, including increased CD4+ T lymphocyte counts and improved lymphokine-activated killing cell activity, which suggests protective and modulatory properties for the horse’s immune system.

Study Methodology

• The study was conducted on healthy young horses, from which samples were taken on days 0, 7, and 14.
• Propionibacterium acnes (P. acnes), sold under the brand name Eqstim, was administered intravenously on days 7, 9 and 11.
• To assess the immune function of the horses, researchers collected two types of samples: blood samples through jugular venipuncture, and bronchoalveolar lavage (BAL) fluid for pulmonary leukocytes recovery.

Findings

• Fever was observed in horses on days 8 and 10, indicating an immune response.
• After P. acnes administration, researchers noticed an increased total white blood cell count on day 14, compared to days 0 and 7.
• Contrastingly, the total BAL fluid cell count decreased on day 14, characterized by a reduction in lymphocyte and macrophage counts.
• The study found an increase in the proportions of CD4+ T lymphocytes in peripheral blood, and CD4+, CD5+, and MHC II lymphocytes in BAL fluid on day 14.
• Nonopsonized phagocytic activity in peripheral blood and lymphokine-activated killing cell activity in peripheral blood and BAL fluid leukocytes were both enhanced on day 14 after P. acnes administration.
• However, P. acnes administration did not change the serum concentrations of immunoglobulins IgG and IgM.

Significance of the Research

• The increased CD4+ T lymphocyte counts and enhanced lymphokine-activated killing cell activity suggest that P. acnes administration stimulates the immune system and alters immune functions in horses.
• The decrease in pulmonary cellular count might indicate a potential therapeutic benefit of P. acnes in the treatment of non-specific respiratory diseases in horses.
• This study helps broaden the understanding of the immunostimulant and immunomodulatory effects of P. acnes, potentially leading to improved treatment of respiratory issues in equine health.