Invariant NKT Cells as Initiators, Licensors, and Facilitators of the Adaptive Immune Response

In the past, the neural reflex arc provided immunologists with a useful analogy for understanding the adaptive immune response (Fig. 1). A revisit to the concept of the immune reflex arc, in which the immune response is divided into an afferent limb, central processing mechanism, and efferent limb, may help us understand where and how various innate immune cells function. Originally, the cells that were thought to be involved in the afferent limb were macrophages (Mφ) and DCs that had taken up and perhaps processed antigen before transporting the antigen to the secondary lymphoid organ. The central processing mechanism involves the interaction of T and B cells and the antigen-presenting cells (DCs) to generate effector cells and molecules. The efferent limb of the immune reflex arc begins once the effector cells and molecules leave the lymphoid tissue and enter the efferent lymphatics and...