Induction of apoptosis by strains of M. tuberculosis. Monocytes from 6 donors were infected with strains and co-cultured for 72 hours. Apoptosis was determined by ELISA for nucleosomal fractions in culture supernatants. Results for each subject were normalised to unstimulated cells to generate an enrichment factor. The mean + SD of this enrichment factor is shown. Although the Δ19 strain tended to induce less apoptosis than H37Rv and Δ19::19 none of the differences were statistically significant.