Santa's Little Helper of "TV Guide". This issue was released with 24 different covers, all featuring different characters from "The Simpsons". Santa's Little Helper Santa's Little Helper is a recurring character in the American animated television series "The Simpsons". He is the pet greyhound of the Simpson family. The dog was introduced in the first episode of the show, the 1989 Christmas special "Simpsons Roasting on an Open Fire", in which his owner abandons him for finishing last in a greyhound race. Homer Simpson and his son Bart, who are at the race track in hope of winning some money for Christmas presents,
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,