Prolonged exposure to <i>M. bovis</i> BCG affects NK cell cytoxicity.

<p>Human NK cells isolated from the blood of healthy donors were cultured in the presence or absence of interleukin-2 (IL-2) (100U/ml) and/or <i>M. bovis</i> BCG (MOI 1:4). A) Cell supernatants from a single donor were assayed for IFN-γ every 24h and for up to 96h post-culture. B) Recovered NK cells were assayed for cytotoxicity against the erythroleukemia line, K562, at an effector:target ratio of 1:1. C) and D) Bar graph showing significant reduction of NK cell cytotoxicity against K562 cells in the presence of IL-2 following 72h of exposure or not with mycobacteria from independent experiment and donor (Mean +/- SD of technical triplicates, unpaired t test, **p<0.01).