3.4 Perforin levels were decreased in cytotoxic T cells

To investigate the ability of cytotoxic lymphocytes to clear virus-infected cells, we analyzed the expression of one of the major cytotoxic effector molecules, perforin, in cytotoxic lymphocyte populations, CD8αα+ and CD8αβ+ αβ T cells, and effector γδ T cells (Figure 5).
In contrast to all other investigated tissues, perforin expression in CD8αα+ T cells was increased 7 dpi in blood and spleen of domestic pigs (Figure 5A, B). Strikingly, it was reduced 4 dpi and virtually undetectable 5 dpi in the liver and ghLN of domestic pigs (Figure 5C, D). In wild boar, perforin expression decreased 5 dpi in the blood, but was elevated above control levels 7 and 10 dpi in blood, spleen, liver, and ghLN (Figure 5A-D).
CD8αβ+ T cells showed a similar but more pronounced course with a significantly decreased expression of perforin 4 and 5 dpi in domestic pigs as well as wild boar in all investigated tissues (Figure 5A-D). Compared to the perforin expression in uninfected controls, the perforin loss in CD8αβ+ T cells was even more distinct than in CD8αα+ T cells. Perforin expression was back to control levels 7 dpi in all animals. In domestic pigs, another significant decrease of perforin occurred 10 dpi. This second reduction was less pronounced in wild boar.
CD8α+ effector γδ T cells showed a perforin expression comparable to CD8αα+ T cells. In domestic pigs, the perforin expression was increased 7 dpi in the blood (Figure 5A) but remained virtually unchanged in the spleen (Figure 5B). Wild boar showed a reduced perforin expression 5 dpi in blood and spleen. However, this effect was less pronounced as for the other T-cell populations and returned to control levels 7 and 10 dpi (Figure 5A, B). In the liver and ghLN, we detected slight perforin decreases in ghLN 10 dpi but no other significant expression changes in wild boar (Figure 5C, D). In contrast, perforin expression in domestic pigs showed a significant decrease 5 dpi in the liver, and 4 and 5 dpi in ghLN. After the cells regained their perforin expression levels 7 dpi, there was another loss 10 dpi (Figure 5C, D).