What are Reactive Lymph Nodes?
Reactive lymph nodes are small white blood cells that produce antibodies against your own tissues. They have been found in patients with cancer, AIDS, multiple sclerosis, and other diseases. These lymphocytes react to foreign substances or foreign proteins. When they do so, they release chemicals called cytokines into the bloodstream which cause inflammation and pain.
The term “reactive” refers to their ability to react when exposed to something. A “leukemic” reaction means that they are not responding normally to a particular substance or protein.
Lymph nodes are the organs where these immune system cells reside. They produce white blood cells called T-lymphocytes, which attack invading organisms such as bacteria, viruses, fungi and parasites.
They also secrete factors that affect the function of other body systems. For example, they influence the production of red blood cells and platelets.
They may even play a role in controlling your heart rate and breathing rate.
Reactive lymph nodes are usually found at sites where there is an imbalance between normal tissue growth and destruction. The most common site is in the bone marrow, but they can occur anywhere else on your body where your immune system is producing abnormal amounts of inflammatory cells.
The term “reactive” is also used to refer to a reaction caused by an allergic substance or drug. So sometimes people will talk about a person who has undergone an allergic reaction, or has an allergic disease such as asthma.
The word “allergy” itself comes from the Greek word allos meaning, “other” and ergon meaning, “work.” Thus allergy means the alteration of normal work by another substance.
Sometimes referred to as type-2 hypersensitivity, allergic reactions occur when an individual has been exposed to a particular allergen before, but this time the immune system overreacts to it. Allergens are usually airborne, such as dust or pollen, or food substances.
But they can also be drugs such as antibiotics, insect venom or even snake bite toxin.
An allergic reaction causes the immune system to release a type of antibody called Immunoglobulin E (IgE). These antibodies release histamine and other chemicals that lead to inflammation.
This is why people who suffer from allergies experience it in places where allergens enter the body, such as the eyes (allergic conjunctivitis), nose (allergic rhinitis) or airways (asthma).
Anaphylaxis is a severe, potentially life-threatening allergic reaction.
One of the major functions of your immune system is to protect your body from foreign substances such as bacteria and viruses. Most of these invaders enter your body through your skin, your mouth or your lungs.
Your mucous membranes trap the majority of them before they enter your bloodstream, and then you cough or sneeze, ejecting them out of your body.
But some infectious agents are small enough to pass through these barriers, so your immune system has additional layers of protection. One of these is a barrier of skin cells that surround your blood vessels.
They allow nutrients and oxygen in the blood to pass through, but not larger substances such as bacteria and viruses. So the invaders are trapped in a sack made up of the walls of your blood vessels. Specialized white blood cells then surround the infected area and destroy the invaders.
When a pathogen manages to get through your skin barrier, for example by burrowing through it, the first line of defense is your acute inflammation response. Specialized cells release inflammatory mediators such as histamines, serotonin and prostaglandins.
They also attract other white blood cells and cause your blood vessels to dilate. The area swells, which not only traps the pathogen within a localized area, it also makes it harder for it to infect other parts of your body. This is called your innate immune response.
Your innate immune response also includes specialized cells such as macrophages, natural killer cells, neutrophils and dendritic cells. These actively seek out and destroy invaders.
This process, in which white blood cells travel throughout your body looking for pathogens to destroy, is called inflammation. It is part of your innate immune response and occurs over a relatively long period of time.
Acute inflammation can occur after an injury. This is your body’s way of walling off the damaged area and preventing any pathogens from entering your blood stream and infecting your entire body.
If the acute inflammatory response doesn’t eliminate the infectious agents, then chronic inflammation occurs in an attempt to wall them off from the rest of your body. This process is called granuloma, which is Latin for “granules.” It consists of a mass of macrophages surrounding the infectious agent.
If the macrophages fail to eliminate it, a layer of connective tissue forms around it. This process is known as fibrosis or scarring. If it occurs in an area such as the skin, it causes scarring and is responsible for keloids and hypertrophic scars. If it occurs in the lungs, the formation of excess fibrous tissue can restrict the flow of oxygen to the rest of the body. This process is known as pulmonary fibrosis or pulmonary hypertension.
Sometimes the body mistakes harmless substances for pathogens and creates granulomas around them. This is known as a hypersensitivity or allergic reaction.
An example of this is when you have an itchy rash after you touch poison ivy. The poison ivy proteins are trapped by cells in your skin and surrounded by macrophages. These macrophages release inflammatory chemicals such as histamine, which causes the rash.
Your body’s infection-fighting capabilities are not always successful. Sometimes the infectious agents outnumber the white blood cells, sometimes they are mutants that are no longer recognized as foreign and sometimes they are just too powerful.
When the pathogens win, they cause serious diseases such as sepsis, toxic shock syndrome, meningitis, encephalitis and many more. These are known as nosocomial, or hospital-acquired, infections. They often prove fatal.
Even when the immune system wins, it is still possible for the pathogens to win. Every once in awhile, a pathogen gets through the defenses and causes an infection.
This results in a disease such as the common cold or influenza.
The immune system can also be made weaker by stress, lack of sleep, bad nutrition, poor health or even the improper use of antibiotics. This makes you more susceptible to disease and a better host for any pathogens that manage to get through your defenses.
Other defense mechanisms in humans
Besides the innate and adaptive immune responses, there are other ways in which humans defend themselves. One of these is the formation of pus.
Pus consists of dead white blood cells that have managed to engulf the harmful organisms. It also contains inflammatory chemicals such as histamine and interferon. Another defense mechanism is called lysozyme. This is an enzyme found in human tears and saliva that breaks down the cell walls of some bacteria.
Viruses can affect the human defense mechanisms including the innate and adaptive immune responses. People with AIDS experience a severe suppression of the adaptive immune response.
The human defense mechanisms can also be overwhelmed by the sheer number of infectious agents, especially in the case of bioterrorism.
Biofilms are communities of microorganisms that have a jelly-like coating. They are more resistant to antibiotics and the human defenses than the individual microorganisms themselves.
Biofilms are more commonly found in medical settings including catheters and water systems.
Antibiotics are used to treat bacterial infections and have no effect on viruses. They can also cause allergic reactions in some people.
Recurring infections could be a sign of an underlying problem such as a pituitary disorder or hypothyroidism.
Vaccines are available to treat or prevent some of the most common infectious diseases. These vaccines trick your immune system into thinking that it has fought off an infection.
This prepares your body to fight off a real infection should you encounter one in the future. Some of the vaccines are effective for a lifetime while others are only effective for a few years.
Sources & references used in this article:
IL-4–producing CD4+ T cells in reactive lymph nodes during helminth infection are T follicular helper cells by IL King, M Mohrs – Journal of Experimental Medicine, 2009 – rupress.org
L-selectin-negative CCR7− effector and memory CD8+ T cells enter reactive lymph nodes and kill dendritic cells by G Guarda, M Hons, SF Soriano, AY Huang… – Nature …, 2007 – nature.com
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Prevalence of follicular lymphoma in situ in consecutively analysed reactive lymph nodes by T Henopp, L Quintanilla‐Martínez, F Fend… – …, 2011 – Wiley Online Library
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Evaluation of metastases and reactive lymph nodes in Doppler sonography using an ultrasound contrast enhancer by J MÄURER, C Willam, R Schroeder… – Investigative …, 1997 – journals.lww.com
Characterization of immature sinus histiocytes (monocytoid cells) in reactive lymph nodes by use of monoclonal antibodies by PC de Almeida, NL Harris, AK Bhan – Human Pathology, 1984 – Elsevier
CD40L+ CD4+ memory T cells migrate in a CD62P-dependent fashion into reactive lymph nodes and license dendritic cells for T cell priming by A Martín-Fontecha, D Baumjohann, G Guarda… – The Journal of …, 2008 – rupress.org
Extracellular matrix proteins and integrin receptors in reactive and non-reactive lymph nodes. by E Castanos-Velez, P Biberfeld, M Patarroyo – Immunology, 1995 – ncbi.nlm.nih.gov