How our immune system protects us by raising body temperature

 Source: Roz Dhan "Seeker95"

How our immune system protects us by raising body temperature

In 1917 doctors propose an outlandish treatment for syphilis, the curable bacterial infection that had ravaged Europe for centuries. Infect patient suffering from the later stages of syphilis with the parasite that causes deadly malaria but curable mosquito-borne disease, in the hope that malarial fever clears syphilis. And administered quinine to cure malaria. If everything works according to plan the patient would be left alive and free of both diseases. This killed some 15% of patients but for those who survive, it seems to work. It actually became the standard treatment for syphilis until penicillin was used decades later. And its driving force was fever, there are many mysteries around the fever but we do not know that all the mammals, some birds even the few invertebrate and plant species feel fevers heat. It has persisted for over 600 million years of evolution but it has a significant cost.  For every degree Celsius of temperature increase in the human body, there is a 12.5% increase in energy requirement. The equivalent is about 20 minutes of jogging for some. So why and how our body produces a fever?



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Our body's core temperature is maintained by thermoregulation, a set of processes that usually keep us around 37-degree Celsius. This mechanism is controlled by the brain's hypothalamus, which detects minute temperature shifts and sends signals throughout the body accordingly. If you too hot then the hypothalamus produces signals that activate your sweat glands or make your blood vessels dilute moving blood closer to the skin surface. All of which releases heat and cools you off. And if you are too cold then your blood vessels will constrict, and you may start to shiver which generates heat. Yor body will disrupt it usually temperature equilibrium to induce a fever which usets in about 38-degree Celsius meanwhile it has mechanisms in place to prevent it from exceeding 41-degree celsius when organ damage could occur. An immune cell that is fighting infection can induce a fever by triggering a biochemical cascade that ultimately instruct with your hypothalamus to increase your baseline temperature. Your body then gets to work, to meet its new set point using the mechanism it would to generate heat when cold until it reaches these new temperatures, you feel comparatively cool which is why you might experience chills. But why your body does this.

It seems that fever's main effect is in repeatedly inducing a whole-body immune response. Upon exposure to raised internal temperature, some of your cells release heat shock proteins or HSPs, a family of molecules that are produced in response to a stressful condition, these proteins aid Lymphocytes, one of several kinds of white blood cells that fight pathogens to travel more rapidly to infection sides, HSP do this by enhancing the stickiness of lymphocytes enabling them to squeeze to blood vessels wall. So, they can reach the area where the infection is razing. In case of viral infections, HSPs tell nearby cells to stop their protein production which limits the ability of the virus to replicate this turns the viruses spread because they depend on host replicated machinery to reproduce. It also protects surrounding cells from damage since some viruses spread by rupturing the host cell, which can lead to large-scale destruction the buildup of detritus, and potentially even organ damage. The ability of HSP is to protect the host cells and enhance immune activity can limit the pathogen of destruction inside of the body. But for all, we know about fever role in immune activation some clinical trials have shown that fever suppresser drugs don't worse the symptom or recovery rate. This is why no definitive rule on whether to suppress a fever or let it be rise. The doctor decides on a case-by-case basis, the fever duration, and intensity as well as their patient's immune status, comfort level, and age all play a vital role in their choice of treatments. And if they do to let a fever ride, they likely prescribe rest and plenty of fluid to prevent dehydration.

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