Santa's Little Helper and is the center of the plots of several episodes. During the course of the show, he has fathered litters of puppies, passed obedience school, had surgery for bloat, replaced Duffman as the mascot for Duff Beer, and been trained as a police dog at Springfield's Animal Police Academy. Some of the episodes that focus on Santa's Little Helper have been inspired by popular culture or real experiences that staff members of the show have gone through. Although cartoon animals are often anthropomorphized, Santa's Little Helper generally exhibits canine behavior. Cast member Dan Castellaneta currently provides the dog's sounds on
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,