In human disease, alterations in numbers of regulatory T cells - and in particular those that express Foxp3 - are found in a number of disease states.
In mice, a Foxp3 mutation (a frameshift mutation that result in protein lacking the forkhead domain) is responsible for 'Scurfy', an X-linked recessive mouse mutant that results in lethality in hemizygous males 16 to 25 days after birth [REF].