The role of Fever in Infection and Inflammation

Fever or hyperthermia is the elevation of body temperature above normal. A normal healthy adult have a normal body temperature ranging from 36.5 C to 37.5 C. Our body temperature is controlled by the hypothalamus. Fever is considered to be the hallmark sign of infection   Fever is the temporary increase in the body's temperature, in response to some disease or illness. Much like other fundamental aspects of human biology, core body temperature is regulated closely by intricate control mechanisms, involving a complex interplay of autonomic, endocrine, and behavioral responses. The hypothalamus is central to this process, functioning as a thermostat, controlling thermoregulatory mechanisms.

Fever is an almost universal phenomenon of illness, particularly local inflammatory processes, noninfectious as well as infectious. It is considered a defense against disease. High body temperatures intensify the effect of interferons. A high body temperature speeds up the body’s reactions and may help the body tissue repair themselves more quickly. It is thought to be caused by the release of endogenous pyrogens from macrophages and possibly from eosinophils, which are activated by phagocytosis, endotoxins ,immune complexes, and other products. Thus, fever help in the healing process. 
The role of fever in inflammation and infection is it acts as the "alarm" for us human to know that something is not right with our body. It signals us that there is already a pathogen inside our body. And that our body is already fighting it. 

In theory, fever can aid or help host defense. Fevers may be useful to some extent since they allow the body to reach high temperatures, causing an unbearable environment for some pathogens. Also, White blood cells rapidly proliferate due to theThough fever may be categorized as a symptom, it also act as a "helper", that is its role.

The presence of inflammation does not always correlates with the presence infection. Infection happens when there is a viable organism capable of causing a disease in a person. There are several factors that should be taken in consideration in the invasion of infectious agents to a host. Such factors like virulence of organism, number of invading microorganisms, the ability of the host to resist infection, the host's defense mechanism and the presence of special types of barriers, contribute in the causation of infection..

The role of fever in inflammation and infection is actually unclear. Although it is obvious that fever can cause considerable discomfort and even death if very high and uncontrolled, several studies have shown that fever can actually be quite beneficial at certain points. According to our module, an increase in body temperature would mean an increase in the metabolism therefore causing the bone marrow of the body to produce more antibodies than usual at a faster rate. Other studies suggest that some microorganisms/viruses cannot thrive on high temperature environment thus, preventing infection. Also, fever serves as an indicator that our body's immune system is working for us and it is usually a determining factor for people to seek medical help.

Therefore, fever is one of the defense mechanisms that the body utilizes to warn on possible threats of impending disease. And this is why fever plays an important role in the process of inflammation and infection

Fever in inflammation and infection and Modules 1-3 of Advanced Pathophysiology by University of the Philippines Open University

Module 1 (Adaptive and Regulatory Mechanism)

Homeostasis refers to the self regulating process of the body and the maintenance of these process in equilibrium. 

Temperature is ultimately regulated in the hypothalamus. The normal temperature is 36.5–37.5 °C, whether the caused of change in temperature is inside or outside of the body, the body will always do something to maintain its homeostasis. 

Example of this is the negative feedback mechanism. When the set point is raised, the body increases its temperature through both active generation of heat and retaining heat. Vasoconstriction both reduces heat loss through the skin and causes the person to feel cold. If these measures are insufficient to make the blood temperature in the brain match the new setting in the hypothalamus, then "shivering" begins in order to use muscle movements to produce more heat. When the fever stops, and the hypothalamic setting is set lower; the reverse of these processes (vasodilation, end of shivering and nonshivering heat production) and "sweating" are used to cool the body to the new, lower setting. From Figure 1-4 (Effect of temperature change on the negative feedback mechanism), we can clearly see what shivering and sweating roles are. 

Adaptive and regulatory mechanisms, we've learned that our body is dynamic and is always in adjustment with its environment to maintain balance. Although we agree that our bodies are almost the same in terms of its composition and structures, different intrinsic and extrinsic factors differentiates us from the rest of the population. Balance starts from the cellular level, and we've learned that healthy cells means a healthy body. Our body is incredible, it can adapt to various situations. It has its own "self-government" with its own rules and regulations and all of the cells have their designated functions. Several regulatory mechanisms govern our bodies so that we maintain homeostasis. It is amazing to know that when our bodies are under attack, i.e. infection or inflammation, negative feedback mechanisms take effect and the brain signals the body to take necessary actions/processes to fight the infection and repair the damage. Having an understanding about this mechanisms can help us better understand how our bodies work (how inflammation works, its functions, it benefits to the body) and thus, adapt our actions/interventions to support/promote the body's natural ways of healing/repairing itself.

Module 2 (Cellular Functions: An Overview)

In this module, we learn the cellular changes and aging. We learn that thinning of the epithelium and decreased in subcutaneous fat could affect regulatory of temperature. Decreased in subcutaneous fat lessen the skin's insulating ability. This will lessen the affect of "shivering". Also, aged cells decreased the number of sweat glands in the skin. Thus, decreasing the ability to eliminate heat through evaporation. I think this will lessen the effect of "sweating".

With this data, we can tell that cell aging thus affect the process of conserving and eliminating heat. 

Module 3 (Alterations in Protective Mechanism: Inflammation and Infection)

Fever arise when there is inflammation and infection. Thought in some cases, there are no fever present. The mechanism of fever is a defense reaction by the body against infection. When bacteria or viruses invade the body and causes tissue injury, one of the immune system's response is to produce pyrogens. A pyrogen is a substance that induces fever. These can be either internal (endogenous) or external (exogenous) to the body. The bacterial substance lipopolysaccharide (LPS), present in the cell wall of some bacteria, is an example of an exogenous pyrogen. These chemicals are carried to the brain, where they disturb the functioning of the hypothalamus. 

The cellular response to injury has again proven to us the beauty and complexity of the human body. The module stated some examples of protective mechanisms used by the body to guard itself from harm. Although most of the examples given were trivial,  we were actually surprised to know that fever can actually be a form of protective mechanism. Before, all I know is that fever is the universal sign of infection and it signal us that something is wrong with our body; that our immune system is working and defending us from "invaders". In my opinion, the reason perhaps why phagocytic cells release endogenous pyrogens during inflammation/infection is to signal the body that they need back-up. Let me explain it using this analogy:

Our body is like a country; with the brain as its president. The cells are his constituents. The organs are like his cabinet secretaries. Now, during an invasion (infection) the local police(sensory neurons) will now try to suppress the invasion locally (local inflammation). With the help of the local police (phagocytic cells) on site, they will try to kill the invaders (bacteria). However, the invaders are too strong for the local police, therefore, the local police will send signal (endogenous pyrogens) to the president, through one of his office (the hypothalamus) to ask for back-up. What the president would do then is to order his secretary of defense (immune system) to send and produce more back-up as well as contingency measures(thru the bone marrow creating more cells) to repair the damage done. The secretaries (body organs) complies with the order by increasing their metabolic rate (to produce the needed "soldiers" and "materials" as well as to speed up transport) and thus produce heat which in turn causes fever.