Santa's Little Helper reason he stopped performing as Santa's Little Helper was because "The producers thought... 'Hmmm, Dan barks pretty good, and we are already paying him and he seems to like doing the dog thing... why do we need to pay Welker who comes in here, spends less than an hour, eats all the doughnuts, refuses to come to rehearsals... let's just give the damn dog to Dan!'" Santa's Little Helper has become a well-known dog because of his appearances in the series. A writer for "The Grand Rapids Press" wrote in 2002 that "we all know who Homer, Marge, Bart, Lisa
T helper cell because such knowledge may be very useful in the treatment of disease and in increasing the effectiveness of vaccination. Proliferating helper T cells that develop into effector T cells differentiate into two major subtypes of cells known as T1 and T2 cells (also known as Type 1 and Type 2 helper T cells, respectively). T1 helper cells lead to an increased cell-mediated response, typically against intracellular bacteria and protozoa. They are triggered by IL-12 and their effector cytokines are IFN-γ and IL-2. The main effector cells of T1 immunity are macrophages as well as CD8 T cells, IgG B cells,