Cells were infected with C. trachomatis and treated with 1 μg/ml of azithromycin at 20 h PI in order to clear the infection, as well as to evaluate whether azithromycin might have an effect on the increased expression levels of the immune regulatory genes IDO1, TGF-β1 and FoxP3, observed in women post antibiotic treatment. Here, IDO1 is linked to infection.