Conjunctival FOXP3 in trachoma: T cells not specified.

The article by Faal et al. [1] describes differences in the level of FOXP mRNA expression in the conjunctiva of patients with Chlamydia trachomatis infection. The authors suggest that their results may indicate a role for regulatory T cells in the resolution of conjunctival immune response, since FOXP mRNA remained elevated even if clinical disease signs were present in the absence of infection.

But suggestions about the function of regulatory T cells in diseases based only on the quantification of FOXP mRNA should be considered with great caution. According to the current state-of-the-art it is well established that FOXP does not specify human regulatory T cells since it is expressed at the mRNA and the protein levels to different extents protein at [2-5]. Thus, without quantification of FOXP3 the single cell level in conjunction with reliable markers of human regulatory T cells, e.g., the recently identified lack of CD127 expression on regulatory T cells [6,7], the potential contribution or association of regulatory T cells with a disease cannot be assessed.