Santa's Little Helper the show, but voice artist Frank Welker has also voiced him. Santa's Little Helper has become a popular character following his appearances on "The Simpsons". He ranked 27th in Animal Planet's 2003 television special "50 Greatest TV Animals" that was based on popularity, name recognition, and the longevity of the shows. He has also been featured in merchandise relating to "The Simpsons", such as video games, board games, and comics. Santa's Little Helper is a greyhound that appears on the animated television series "The Simpsons" and is the pet dog of the Simpson family. He can often be seen 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,