Fig. 3.

Leukotoxicity of A. actinomycetemcomitans strains with different leukotoxin promoter types on cultures of PMA-differentiated THP-1 cells. Strains: 456A1 (novel), HK1651 (JP2), Y4 (non-JP2), and NCTC9710 (non-JP2). The THP-1 cells were exposed for 2 hours with 10% of a NaCl surface extract based on a bacterial density of OD 10 at 600 nm. Mean and standard deviations from two different experiments with four replicates in each are shown. (a) Cell lysis as a percentage of LDH release in relation to that of a triton-lysed control sample. (b) Viability as a percentage of neutral red uptake in relation to a plane control sample.