Table 3.
Analyses of CD8+ T cell clones derived from animals immunised with T. parva for reactivity with defined epitopes in the Tp1 and Tp2 antigens
| Animal (MHC type) | Clones tested | Numbers of positive clones and levels of cytotoxicity detected on T. parva-infected and peptide-pulsed target cellsa) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Infected | Tp1214–224 | Tp249–59 | Tp298–106 | ||||||
| Positive | Cytotox | Positive | Cytotox. | Positive | Cytotox. | Positive | Cytotox. | ||
| 468 (A18/A18) | 90 | 10 (11%) | 6–10% | 72 (81%) | 8–100% | ||||
| 641 (A18/A18) | 87 | 52 (59%) | 6–33% | 69 (78%) | 7–100% | ||||
| 592 (A10/A10) | 83 | 53 (64%) | 9–74% | 49 (59%) | 21–96% | 3 (4%) | 56–99% | ||
| 1011 A10/A10 | 89 | 85 (95%) | 7–79% | 66 (74%) | 9–100% | 2 (2%) | 73–75% | ||
CD8+ T cell lines were tested for cytotoxicity using a 4-hour 111In release assay. Target cells consisted of autologous T. parva-infected cells (infected) and autologous T. annulata-infected target cells incubated with 1 ug/mL of the respective peptides. The number and percentage of positive clones (positive) and the range of levels of cytotoxicity of positive clones (cytotox.) are shown for each set of clones on each target cell. A standard cut-off of >5% specific cytotoxicity was used to define positive clones. In all assays, this was well in excess of 3 standard deviations above the mean background release value of the respective target cells and was also well in excess of 3 standard deviations above the mean levels of cytotoxicity obtained with MHC-mismatched T. parva-infected targets (as a control for infected targets) and unpulsed T. annulata-infected target cells.