once the production of cortisol matches the stress induced on the immune system. But in a severe infection or in a situation where the immune system is overly sensitized to an antigen (such as in allergic reactions) or there is a massive flood of antigens (as can happen with endotoxic bacteria) the correct set point might never be reached. Also because of downregulation of Th1 immunity by cortisol and other signaling molecules, certain types of infection, (notably Mycobacterium tuberculosis) can trick the body into getting locked in the wrong mode of attack, using an antibody-mediated humoral response when a cellular response is needed. Lymphocytes are the antibody-producing cells of the body, and are thus the main agents of humoral immunity. A larger number of lymphocytes in the lymph nodes, bone marrow, and skin means the body is increasing its humoral immune response. Lymphocytes release antibodies into the bloodstream. These antibodies lower infection through three main pathways: neutralization, opsonization, and complement activation. Antibodies neutralize pathogens by binding to surface adhering proteins, keeping pathogens from binding to host cells. In opsonization, antibodies bind to the pathogen and create a target for phagocytic immune cells to find and latch onto, allowing them to destroy the pathogen more easily. Finally antibodies can also activate complement molecules which can combine in various ways to promote opsonization or even act directly to lyse a bacteria. There are many different kinds of antibody and their production is highly complex, involving several types of lymphocyte, but in general lymphocytes and other antibody regulating and producing cells will migrate to the lymph nodes to aid in the release of these antibodies into the bloodstream. Rapid administration of corticosterone (the endogenous type I and type II receptor agonist) or RU28362 (a specific type II receptor agonist) to adrenalectomized animals induced changes in leukocyte distribution. On the other side of things, there are natural killer cells; these cells have the ability to take down larger in size threats like bacteria, parasites, and tumor cells. A separate study found that cortisol effectively disarmed natural killer cells, downregulating the expression of their natural cytotoxicity receptors. Interestingly, prolactin has the opposite effect. It increases the expression of cytotoxicity receptors on natural killer cells, increasing their firepower. Cortisol stimulates many copper enzymes (often to 50% of their total potential), including lysyl oxidase, an enzyme that cross-links collagen and elastin. Especially valuable for immune response is