Cell-mediated immune response to Babesia equi-transformed lymphoblastoid cells in vitro.

This research investigates how the peripheral blood lymphocytes (PBL) of horses proliferate when exposed to Babesia equi-transformed lymphoblastoid cells. This immune response was examined in both autologous and allogeneic one way mixed lymphocyte reactions. It was found that older horses had a more effective immune response to the parasite.

Autologous and Allogeneic One Way Mixed Lymphocyte Reactions

• The researchers tested the capacity of equine peripheral blood lymphocytes (or white blood cells) to proliferate in the presence of Babesia equi-transformed lymphoblastoid cells, an infectious agent that can cause equine babesiosis.
• In autologous lymphocyte reactions, the responder and stimulator cells come from the same individual. These reactions demonstrated a high rate of 3H-thymidine intake, a marker of DNA replication and thus, cell proliferation.
• In allogeneic lymphocyte reactions, the responder and stimulator cells come from different individuals of the same species. These also demonstrated high levels of 3H-thymidine intake. However, the amount was lower than in autologous reactions suggesting a difference in the immune response between the same individual and between different individuals.

Proliferation Triggered Only by Intact Infected Cells

• The study found that the proliferation of PBL could only be initiated by intact parasitized cells. When infected cells were broken down, they did not trigger the same immune response.

Difference in Immune Response Due to Age

• The PBL from ponies of different ages were tested for their ability to impede the in vitro growth of culture cells when applying cell co-cultivation, a technique where different types of cells are grown together. The results indicated that PBL from older ponies more effectively inhibited culture schizont growth – the asexual reproduction of the parasite, compared to those from young ponies.
• However, by day 35 post-infection, only PBL from two of the older ponies continued to show an inhibitory effect indicating there may be variation in the immune responses depending on the duration of the infection.

Discussion of Findings

• The possible mechanisms of recognition of effector cells on target cells are discussed. Effector cells are a type of immune cell that carries out an immune response once they recognize a target cell. Determining how these cells recognize their targets can be crucial for understanding the immune response to infections like Babesia equi.