On 2015 Oct 05, Klaus Okkenhaug commented:

In their discussion, Louie and colleagues suggest that mesenteric B cells may inhibit Treg and that idelalisib dysregulates Treg by inhibiting B cell differentiation. Not only is this argument internally inconsistent, but also ignores the potential direct effect of idelalisib on Treg. PI3Kδ-deficient mice develop colitis Okkenhaug K, 2002, PI3Kδ-deficient Treg fail to prevent colitis Patton DT, 2006, and there is a T cell-intrinsic role for PI3Kδ required for effective suppression of CD8⁺ T cells Ali K, 2014. It is therefore reasonable and more parsimonious to sugest that idelalisib causes enterocolitis through a direct effect on Treg. In addition, if depletion of B cells were the main mechanism behind idelalisib-induced colitis, then surely rituximab would have a similar or greater effect as this is a more effective way of depleting B cells.

On 2015 Oct 05, Klaus Okkenhaug commented:

In their discussion, Louie and colleagues suggest that mesenteric B cells may inhibit Treg and that idelalisib dysregulates Treg by inhibiting B cell differentiation. Not only is this argument internally inconsistent, but also ignores the potential direct effect of idelalisib on Treg. PI3Kδ-deficient mice develop colitis Okkenhaug K, 2002, PI3Kδ-deficient Treg fail to prevent colitis Patton DT, 2006, and there is a T cell-intrinsic role for PI3Kδ required for effective suppression of CD8⁺ T cells Ali K, 2014. It is therefore reasonable and more parsimonious to sugest that idelalisib causes enterocolitis through a direct effect on Treg. In addition, if depletion of B cells were the main mechanism behind idelalisib-induced colitis, then surely rituximab would have a similar or greater effect as this is a more effective way of depleting B cells.