FIG 6.
Pretreatment of macrophages with 1,25-dihydroxyvitamin D3 (1,25D3) increases GAS cytotoxicity. THP-1 macrophages were pretreated with 20 nM 1,25D3 for 24 h before being infected with GAS 854, 854Δslo, 854ΔhasB, 854csrSTM, 854ΔcsrR/ΔhasB, or 854ΔcsrR/ΔhasB/Δslo. (A) Supernatants were assayed for LDH release as described above; (B) intracellular GAS were measured. GAS strain designations are as in Fig. 2. Results of a single representative experiment with five (A) or three (B) replicate measurements are shown. *, P < 0.05; **, P < 0.01; ***, P < 0.001. NS, not significant.