Equine cell-mediated immune response to Rhodococcus (Corynebacterium) equi.

This research article focuses on the study of how horse cells react to Rhodococcus (Corynebacterium) equi, a bacterium that can cause diseases in these animals. Through test methods such as lymphocyte blastogenic assays, the study explores the role of cell-mediated immunity in how the equine immune system interacts with the bacterium.

Method of Research

• The research utilized a lymphocyte blastogenic assay, an in vitro experiment that measures cell proliferation. This method was used to serve as a representation of cell-mediated immunity – a type of immune response that involves the activation of certain immune cells.
• Lymphocytes, a type of white blood cell, were taken from a group of ponies. Initially, these cells showed no response to R equi antigens, suggesting a lack of immunity to the bacterium.

Experimental Inoculation and Resulting Responses

• Six ponies were divided into two groups and each group was then exposed to live R equi in different ways – either subcutaneously (under the skin) or through their noses and throats. Another group of four ponies were left unexposed to the bacterium to serve as a control group.
• The lymphocytes from all the inoculated ponies revealed a mitogenic response (a response related to cell division and growth) to R equi antigens, indicating an immune response to the bacterium. However, the lymphocytes from the unexposed ponies did not show any response, which was expected.
• Furthermore, all inoculated ponies developed what is known as delayed-type hypersensitivity reactions after they were given R equi antigen intradermally, or inside their skin. These types of reactions are generally a sign of cell-mediated immunity.

Further Experimentation and Findings

• In the second phase of the study, lymphocytes from horses in herds with endemic R equi infections were used in the blastogenic assays.
• The results showed that several of these animals had significant cell-mediated responses to the bacterium, which was signified by a stimulation index greater than 2, indicating the activation of immune responses.
• However, the researchers found no clear correlation between the immune response and clinical history of the animals, suggesting that cell-mediated immunity to R equi does not necessarily correspond to an animal’s past interactions with the bacterium.

Conclusion

• From these results, the researchers concluded that cell-mediated immunity plays a role in how the horse immune system interacts with R equi, but the relationship is not linked in a straightforward manner with an animal’s clinical history.