KIT and infectious disease: However, recent studies using two or more mast cell-deficient Kit mutant mouse strains and/or mutant mouse strains with unperturbed c-Kit function revealed a more complicated picture: depending on the nature of the mutation resulting in a mast cell deficiency as well as the type and severity of infection, mast cells can have no effect, aggravate, or attenuate inflammation and infectious disease severity (25–28).