Final answer:
The local effects of IL-6 include promoting wound healing during stress, whereas systemically, IL-6 can lead to symptoms like lethargy, muscle pain, and nausea, as well as severe consequences like septic shock in cases of high concentrations. IL-6 also modulates brain functions related to stress and cognitive processes through brain-immune system communication.
Step-by-step explanation:
The local and systemic effects of interleukin-6 (IL-6) are diverse and pivotal in both the immune system's response to stress and pathogen defense. Locally, IL-6 contributes to the immune system by promoting wound healing, mainly because it is part of the immune response that is triggered during an acute stress reaction. This is especially relevant because peripheral IL-6 levels during stress are related to the experience of emotions like anger, which can result in physiological changes conducive to confronting and healing from physical challenges.
Systemically, IL-6 can have profound effects on the body during states of inflammation or infection. It can influence behaviours by acting on the nervous system, leading to symptoms like lethargy, muscle pain, and nausea - an adaptive response to conserve energy and limit the spread of infection. Elevated systemic levels of IL-6 can potentially lead to severe conditions like septic shock, characterized by widespread edema, a drop in blood pressure, and, if uncontrolled, multiple organ failure and death.
Furthermore, there is a bidirectional communication between the brain and the immune system, with cytokines like IL-6 modulating brain functions under physiological conditions. This can impact various neural processes, including those related to stress, sickness behavior, and cognitive functions like learning and memory.