The Lymphatic System and Mononucleosis

by Robert Tallitsch, PhD | October 18, 2023

Video explaining the lymphatic system and mononucleosis with a patient example!

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Mononucleosis (also termed infectious mononucleosis or “mono”) is a common disease among adolescents and young adults, including college students. It is often called “the kissing disease” because it spreads easily through body fluids, such as saliva, and therefore can be spread through kissing. It can also be spread by sharing food utensils or by sharing a glass with someone who has mononucleosis. However, mononucleosis is not as contagious as many diseases caused by a virus, such as the common cold.

Because mononucleosis typically involves enlargement of the cervical lymph nodes, and may also cause enlargement of the spleen, this Brain Builder will briefly review the anatomy of the lymphatic system. We will also discuss the symptoms, possible causes, and treatment options for Mononucleosis.

Lymphatic System

The lymphatic (lymphoid) system is functionally a part of the cardiovascular system. The lymphatic system transports and monitors a fluid called lymph. Lymphatic vessels carry the lymph from the periphery to the lymphatic system, and then ultimately to the veins of the cardiovascular system. Lymph is composed of interstitial fluid, macrophages, and lymphocytes.

The functions of the lymphatic system are:

Maintenance of normal blood volume and the elimination of variations in the local composition of the interstitial fluid.
Provide an “alternative route” for the transport of wastes, nutrients, and hormones.
Production and maintenance of lymphocytes that are involved in the body’s acquired immune responses.

Lymphatic Tissues and Organs

Lymphatic organs are encapsulated within a layer of connective tissue and are composed of tightly organized lymphatic cells. Examples of lymphatic organs are the tonsils, thymus, spleen, and lymph nodes.

Lymph nodes are small encapsulated lymphatic organs located along the course of lymphatic vessels throughout the body. Several afferent lymph vessels enter each lymph node, and only one or two efferent lymph vessels exit the node.

Lymph nodes are widely distributed throughout the body — typically in areas that are susceptible to injury or pathogenic infiltration.

Cervical lymph nodes filter lymph originating from the head and neck.
Axillary lymph nodes filter lymph originating from the upper limbs.
Popliteal lymph nodes and inguinal lymph nodes filter lymph originating in the leg and thigh of the lower limb.
Intestinal lymph nodes and mesenteric lymph nodes filter lymph originating within the digestive (gastrointestinal) system.
Abdominal lymph nodes filter lymph originating from the urinary and reproductive systems.

Cells of the Lymphatic System

The cells of the lymphatic system are termed lymphocytes. These cells are responsible for specific (or acquired) immunity. This type of immunity is not inherited at birth; rather it is acquired over time following exposure to pathogens. The two types of specific immunity are artificial or natural. Artificial immunity is acquired through vaccinations, while natural immunity is acquired by everyday encounters and exposures to disease-causing agents and pathogens.

The primary cells of the immune system are termed lymphocytes. These cells are found within the lymphatic and cardiovascular systems, as well as within the interstitial spaces of the body. When a lymphocyte encounters a pathogen, it will initiate an immune response.

There are three classes of lymphocytes: T cells, B cells, and NK cells. Each cell type has distinctive biochemical and functional characteristics.

T cells comprise the largest percentage of lymphocytes. These cells originate in the bone marrow and then migrate to the thymus to become immunocompetent, or activated. When properly stimulated, T cells differentiate into several different cell types that will attack antigens and increase the body’s immune response.

B cells, which are the second most common form of lymphocytes, originate and become immunocompetent within the red bone marrow. Immunocompetent B cells divide and differentiate into either plasma cells (plasmocyte), which secrete antibodies, or Memory B cells. Memory B cells become activated only if the antigen appears again in the body at a later date.

NK cells (also termed Natural Killer cells) attack foreign cells, normal cells infected with a virus, and cancer cells that appear within normal tissues.

Symptoms of Mononucleosis

Mononucleosis is typically caused by the Epstein-Barr virus. The NK cells of the lymphatic system become activated by the virus. The interaction between the NK cells and the Epstein-Barr virus causes the various symptoms of mononucleosis. Symptoms for mononucleosis vary considerably from individual to individual. Mono is typically characterized by some or all of the following symptoms, which may last between ten days to three or more weeks.

Rapid onset of a severe sore throat
Enlarged cervical, axillary, and/or inguinal lymph nodes
Fever
Significant fatigue, which may last between three to six months
Headaches
Muscle aches and weakness
Loss of appetite
Enlarged spleen or liver

Diagnosis of Mononucleosis

A diagnosis of mononucleosis is typically accomplished through an assessment of the patient’s symptoms during a complete physical examination. The physician may also order laboratory tests, including a WBC (white blood cell) count to determine the presence or absence of an infection, and a heterophile antibody test (also termed a monospot test) to determine the presence or absence of antibodies to the Epstein-Barr herpes virus, the most common virus that causes mononucleosis.

Treatment of Mononucleosis

No antibiotics or antiviral drugs have been found effective in the treatment of mononucleosis. In addition, there is no inoculation against the disease. Therefore, treatment typically involves attempting to alleviate the symptoms mentioned above by:

Prolonged rest,
Drinking plenty of fluids,
Use of NSAIDS (nonsteroidal anti-inflammatory drugs) to ease the fever, headaches, muscle aches associated with mononucleosis,
Use of throat lozenges or gargling with salt water to soothe severe sore throats,
Avoidance of physical activity, such as sports, to help reduce strain on an enlarged spleen, if one is present.

Following the alleviation of the symptoms of mononucleosis, the Epstein-Barr virus typically remains dormant in blood cells and cervical lymph nodes throughout a person’s lifetime. The virus may reactivate periodically but seldom causes the reoccurrence of mononucleosis or its symptoms.

Key Terms:

Epstein-Barr virus - The most common virus that causes mononucleosis.

NSAIDS - Nonsteroidal anti-inflammatory drugs

Lymphatic system - The lymphatic (lymphoid) system is functionally a part of the cardiovascular system. The lymphatic system transports and monitors a fluid called lymph.

Lymph nodes - Lymph nodes are small, encapsulated lymphatic organs located along the course of lymphatic vessels throughout the body.

Lymphocytes - The cells of the lymphatic system.

Specific (acquired) immunity - This type of immunity is not inherited at birth; rather it is acquired over time following everyday exposure to pathogens & disease-causing agents.

Artificial immunity - This type of immunity is acquired through vaccinations.

NK-cells - NK cells (also termed Natural Killer cells) attack foreign cells, normal cells infected with a virus, and cancer cells that appear within normal tissues.

T-cells - T cells comprise the largest percentage of lymphocytes. These cells originate in the bone marrow and then migrate to the thymus to become immunocompetent or activated. When properly stimulated, T cells differentiate into several different cell types that will attack antigens and increase the body's immune response.

Heterophile antibody test (monospot test) - A test that determines the presence or absence of antibodies to the Epstein-Barr herpes virus, the most common virus that causes mononucleosis.

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