Figure 4
Bifidobacterium infantis attenuates the baseline secretion of CCL20 in HT-29 cells. (a) Confluent HT-29 monolayers were treated with B. infantis at doses of 1 × 105, 1 × 106, or 1 × 107 colony-forming units/ml, and CCL20 levels were measured after 6 hr. B. infantis caused a dose-dependent inhibition of baseline CCL20 secretion by confluent HT-29 monolayers. (b) Confluent HT-29 cells were treated with 1 × 107/ml live B. infantis or L. salivarius, or an equivalent dose of formalin-killed bacteria. CCL20 levels were measured after 6 hr. Both live and formalin-killed B. infantis, but not L. salivarius, restrained the baseline secretion of CCL20 by HT-29 cells. The data are expressed as CCL20 protein levels relative to untreated control cells and represent the mean ± standard error (n = 5 independent experiments). *P < 0.05 compared with untreated monolayers.