Cellular Immune Responses

Generally speaking, cellular immune responses are comprised of innate and adaptive cell-based immune mechanisms in which all leukocyte subpopulations are involved. This includes effector functions such as phagocytosis, NETosis, and cell-mediated cytotoxicity. The main players are macrophages/monocytes, dendritic cells, granulocytes, NK cells, and cytotoxic T cells. These effector functions can only be executed and controlled through receptor/ligand interactions and by humoral factors produced by leukocytes or somatic cells. Thus, it is hard to draw a static line between cellular and humoral components of the immune systems since one system cannot exist independently from the other. Similarly, adaptive responses cannot be efficiently induced without innate triggers. This chapter describes cellular immune mechanisms in teleost fish and relates them to mammalian immunology.