Regulation of adaptive immune responses by innate cells expressing NK markers and antigen-transporting macrophages

A continuing theme of work done in our laboratory involves regulation of adaptive immune response by innate cells, in general, and immuneregulation by natural killer (NK) and NKT cells, in particular. Studies include work with the lung and the eye. In addition to immune surveillance of tumor cells, the NK cell is often associated with secreting cytokines that contribute to the creation of microenvironments conducive to Th1 responses and with defense mechanisms that lessen the initial infecting viral load. Reported studies show that the NKT cells support both T helper cell responses (type 1 and 2), as well as their being absolutely central to the development of antigen-specific T-regulatory cells involved in peripheral tolerance. Because of the multifunctional capabilities of the NKT cell, we propose that yet another cell, such as the antigen-presenting cell (APC), may influence the effector pathway of the NKT cell. We postulate that the APC that transports the antigen from the entry environment provides both trafficking and activation signals for innate cells in the secondary lymphoid organs. Evidence is presented that macrophage-derived signals selectively recruit NKT cells and bias their cytokine synthesis. Data imply that, just as occurs in immune inflammation, a collection of innate and adaptive immune cells interact within the secondary lymphoid tissue to generate antigen-specific tolerance in the periphery.