Immune responses are tightly regulated by complex interactions of cells and mediators, and has its capability to distinguish “self” molecules from “non-self” molecules. While the enhancement of immune responses can generate autoimmune reactions, decrease of immune responses may lead to immunodeficiency, and shift in immune responses can lead to allergy. Therefore, to maintain the immune system’s homeostasis and tolerance to self-antigens, the body uses a careful balance of stimulatory and inhibitory signaling through specialized cells such as T helper cells (Th1, Th2 and Th17) and Treg cells. For example, T helper cells are able to regulate both the nature and level of the immune response through cytokine signaling.

CD4a (RPA-T4)