Because CFS by itself did not induce cytokine production, TLR9 may have a key role in the context of probiotic-host interactions, and the results suggest that the immunomodulatory effects of L. paracasei product(s) may involve mechanisms that overlap with those associated with CpG [14,2]. The gene discussed is TLR9; the disease is myalgic encephalomeyelitis/chronic fatigue syndrome.