Figure 6.

Cytotoxic and proliferative responses of mycobacterial antigen-specific cytotoxic T-lymphocyte (CTL) clones generated from a human leucocyte antigen (HLA)-B51-matched donor (RG). (A) Both CD8⁺ (a) and γδ⁺ (b) CTL clones mediate mycobacterial-specific cytolytic activity against U937 target cells. U937 target cells were either infected with Mycobacterium tuberculosis (5 colony-forming units [CFU]/cell) (filled bars) or pulsed with an irrelevant antigen, streptokinase-streptodornase (SK-SD) (open bars). Cytotoxicity was measured after 4 hr. Each data point represents the mean percentage cytolysis (± SD) of at least four independent experiments. (B) Proliferative responses of CD8⁺ T-cell clones to (a) soluble purified-protein derivative (PPD) or (b) M. tuberculosis. CD8⁺ T-cell clones were unstimulated, or stimulated with PPD (3 µg/ml) or M. tuberculosis (5 CFU/cell) in triplicate wells in the presence of autologous irradiated peripheral blood mononuclear cells (PBMCs). After 40 hr, cultures were pulsed with [³H]thymidine (1 µCi/well) for 8 hr. Results are expressed as stimulation indices (SI) (in counts per minute [c.p.m.]) and were calculated as follows: $\begin{array}{c}\text{SI}=\left[\right(\text{mean c.p.m. of antigen-stimulated wells})\\ \phantom{\text{s}}÷\left(\text{mean c.p.m. of unstimulated wells}\right)]\end{array}$ Each bar represents the mean SI (± SD) of triplicate wells.