CD4 and aggressive systemic mastocytosis: Hollmann and colleagues claimed that Tregs are more resistant to ASM-deficiency than CD4+Foxp3− T cells, since they observed a reduction in absolute cell numbers of CD4+Foxp3− non-Tregs, but no differences in CD4+CD25+Foxp3+ Treg numbers in Asm-deficient mice and after treatment of mice with amitriptyline (13).