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Figure 2: Perforin is the primary mediator of  injury by CD8+ T cells. Perforin is the primary molecule known to mediate injury by CD8+ T cells. Perforin mediates axonal transection in multiple sclerosis (MS) and correlates with neurological disability. Cytotoxic T cells secrete perforin in the form of granules along with granzymes. This release activates calcium, which results in “poly-perforin” channels on the target cells. This results in holes in the membrane of the target cells, causing leakage of intracellular material, which results in cell death.