Mechanically damaged cells release intracellular substances, resulting in the activation of CD4- and CD8-positive T-lymphocytes. The goal of this investigation was to quantify and compare fractions of activated CD4- and CD8-positive T-lymphocytes, based on the quantity of damaged cells in a given blood sample. Blood samples were mechanically stressed by vortexing intensely. Subsequently, different quantities of distressed blood samples were mixed with samples of fresh, whole blood. Afterwards, the extent of CD4- and CD8-positive T-cell activation was examined in the mixture by flow cytometry. Sine-like curves of T-cell activation were observed for both CD4- (T-helper mediated) and CD8- (cytotoxic) T-cell activation. However, the CD8 activation curve was shifted towards a higher damage ratio, determined by its higher peak value. Mechanical cell damage can generate a T-cell-mediated immune reaction. Therefore, quantities of activated CD4- and CD8-positive T-lymphocytes depend on the extent of cellular damage.