Immunology, as a medical field, is the study of the body’s responses to threats. The word “immune”, as in immune system and immunology, comes from the latin word “immunis”, which means “exempt”. Research efforts in immunology such as vaccination, diagnostic immunology, organ transplantation, etc. have forever changed medical science.
Immunologists study and treat disorders of the immune system. Doctors who study immunology may apply their knowledge in education, medical practice and/or research. To become an immunologist, one must first complete a pre-medical bachelor’s degree. A medical degree comes after that and that should take about four more years of study. Once completed, minimum residency hours must be fulfilled.
An immunology student will typically undertake their residency hours in either pediatrics or internal medicine. Generally, this residency rotation will involve extensive laboratory work, where immunological testing methods and laboratory result interpretation techniques can be studied and applied under supervision. Once residency hours have been completed, membership in an immunology fellowship is a must, during which an applicant gets the chance see patients with immunological disorders, and joins an immunology-related research or begin training in specializing in a particular field of immunology. All of this is done under the supervision and guidance of a licensed immunology physician.
After about three years of training in a fellowship, a medical license may be obtained after passing a licensure exam. The nature of the exam and the requirements to be able to take the exam may differ by country. In America, a board certification from the American Board of Allergy and Immunology(ABAI) must be acquired after getting a medical license. This certification requires a medical degree, a number training hours completed, a medical license, as well as a certification from the American Board of Pediatrics or the American Board of Internal Medicine, depending on where the residency hours were performed and completed.
Continuing education credits must also acquired in order to ensure that immunologists are always up-to-date with new technologies and research. Aside from this, immunologists are also required to pass assessment exams given periodically. The ABAI requires immunologists to complete at least 25 credits of continuing education. Credits may be acquired by attending seminars, publishing articles, or participating or watching internet-based seminars. An immunologist who applies their education in research or education are required to have a Ph. D. Studying to become an immunologist is a long and challenging path, but even after a physician is certified as an immunologist, the rigorous work continues in order to remain reliable and relevant in the field. After all, it is people’s lives that are entrusted to these physicians.
Immunologists who are in contact with patients with immunological disorders are called clinical immunologists. Examples of immunological disorders include allergies, asthma, lupus, immunodeficiency, etc. Clinical immunologists are responsible for the diagnosis and management of such disorders. Their patient interaction is generally on an outpatient basis, meaning the patients are not confined in the hospital.
Aside from this, clinical immunologists also serve as consultants in patient diagnosis. When faced with a threat that cannot be resolved by general immunity, antibodies that are specifically designed to combat particular foreign substances are released by the immune system. The detection of these antibodies allows clinical immunologists to detect the presence of these particular diseases, which would then result in specific treatment methods in the same or other fields.
Diagnostic methods learned in immunology are also used in assessing and performing organ transplantation or blood transfusions. The donor and the receiver must have a certain level of similarity in their antibodies. Otherwise, the receiver’s body will reject the donor’s organ or blood, resulting in much graver consequences.
On the other hand, immunologists who apply themselves in research are at the forefront of vaccine development, disease identification and treatment, among others. Since the development of immunology as a medical practice, several vaccines have been developed for diseases ranging from debilitating to deadly. It is known that the vaccine is the medical invention that saved the most lives and, as such, research is currently being done on more threats to the human body. Among the most notable of these are AIDS and cancer. Research in immunology involves a broad range of techniques designed to decode disease patterns and behaviors and to develop drugs or vaccines that can combat such diseases.
Prior to medical science, diseases were seen as a variety of events tied to culture or supernatural beliefs. Diseases were once viewed as punishments from divine beings, acts of magic, imbalances of energy channels within the body, etc. However, as early as 430 B.C.E., Thucydides, a historian from Athens, provided some evidence for the analysis of plague behavior in his account of the Plague of Athens.
He observed that areas with higher populations produced more plague victims, and at a higher rate of infection. He also observed that physicians in direct contact with plague victims had the highest chance of contracting the plague. Third, he noted that the plague could be transported from one place to another, debunking the prevailing theory at the time that evil airs called Miasma caused widespread diseases. Miasma was believed to be a phenomenon caused by gods, stars, or the weather. The most notable of his observations is the assertion that people who have recovered from the plague are immune to future attacks from the specific plague, but not from other diseases. This is the very first record that shows acquired immunity, a key concept in the modern study of immunology as well as the driving force for the development and application of vaccines.
As for the actual practice of vaccination, as far as the application of a disease in the hope that the body will recover from the disease and create a selective immunity from it, there are records found from 17h century China showing physicians using dried powdered smallpox scabs, applied into the nose. This technique is commonly called variolation. The treatment had a failure rate of about 1-2 percent which resulted in the patient failing to produce selective immunity and possibly causing another epidemic.
The procedure became common in England when Lady Mary Mortley Montague had physicians use the technique on her own children. After that, variolation was performed on six condemned prisoners, all of which survived the operation and would later on prove to be immune to smallpox. The success of the experiment caused variolation to become popular in England, and then to the American colonies soon after.
The development of the first safe vaccine for smallpox is credited to English physician Edward Jenner. He had heard from his early apprenticeship to a country surgeon and apothecary in 1762 that dairymaids were immune to smallpox after contracting cowpox. He was 13 at the time and he continued to hear such tales for many years. In 1796, he decided to apply the tales on James Phipps, an eight-year-old boy. In May 1796, Jenner found a dairymaid who had contracted cowpox, Sarah Nelms. Jenner collected material from the lesions developed on Nelms skin and inoculated Phipps, who then recovered after 10 days. In July 1796, Jenner inoculated Phipps with material from a fresh smallpox lesion. Phipps did not contract the disease. The Latin word for cow is vacca and the Latin word for cowpox is vaccinia. Jenner decided to call this new technique vaccination. Smallpox was a disease that had four types with different fatality rates, reaching to 100% for its hemorrhagic variant. Because of Jenner’s efforts, smallpox has been considered eradicated since 1977.
Evidence for Germ Theory, which asserts that diseases are caused by microorganisms attacking the body, was put forth by German physician Robert Koch and French biologist Louis Pasteur. Prior to Germ Theory, physicians believed that diseases were caused by miasma, or some other non-biological cause. Koch’s work focused on the isolation of anthrax bacilli and its transmission vectors in animals. Later, in 1882, Koch demonstrated germ theory’s applications to human diseases when he isolated the tubercule bacilli, the cause of tuberculosis. Koch also developed criteria to identify the cause of a disease, which are now called Koch’s Postulates. The four Koch’s Postulates are still in use today.
Louis Pasteur, on the other hand, worked initially on a vaccine for chicken cholera. He had accidentally left a flask of chicken cholera bacilli on a bench during the summer, infecting eight chickens. These chickens, although infected, did not appear ill. He later found that these chickens became immune to chicken cholera, leading to the discovery of its vaccine, which he also called a vaccine in honor of Jenner. Pasteur’s work moved on to rabies. He isolated weakened versions of the rabies virus and used a solution of the viruses to save the life of a nine-year-old boy who was bitten by a rabid dog. The boy developed no serious symptoms. This was the first use of the rabies vaccine.
Two theories on how the immune system works would then be developed around the 19th century. The first is the discovery of phagocytes, from the Greek word phago meaning “devour”, by Russian zoologist Élie Metchnikoff. This Cellular Theory of Immunity, while initially rejected in favor of the second theory, is now used in the modern study of immunology. He discovered this while studying the digestive system of starfish larvae. He introduced into the larvae carmine dye particles and splinters, which were soon consumed by cells unrelated to digestion. He believed that these cells are the first line of defense against infection.
The second theory is the Humoral Theory of Immunity. It asserts that substances in the body or introduced into the body is responsible for disease immunity. German physiologist Emil von Behring and Japanese physician Shibasaburo Kitasato first used a serum derived from the blood of animals infected with diptheria and injected it into healthy animals. The healthy animals would prove to be immune to the disease. The serum factors used in this experiment would be recognized as antibodies by 1930.
German physician Paul Ehrlich would then recognize the existence of antibody generators, later called antigens, which triggers the production of antibodies specific to the antigen, much like a lock and key. Ehrlich would be the first to introduce the idea of “self” and “non-self” cell classifications. The Humoral Theory of Immunity would later become the key to diagnostic immunology by providing a basis for the detection of antigens and antibodies as diagnostic techniques.
Much is now known about the immune system. The human body has three lines of defense against germ threats. First, a mucous lining around the digestive tract, the lungs and the genitals stop germs from entering the body. Second, cellular defense systems called phagocytes devour germ threats that slip past the sticky, acid secreting mucous linings of organs. These serve as a general defense system for a wide variety of threats.
Third, the body initiates an adaptive defense system. These cells are initiated if the first two lines of defense fail to respond to the threat. Often, this is slow to react, as the body has to first identify the kind of attack and create the specific kind of antibody to respond to it. These cells operate against threats that the body has not encountered before, and are thus an improvised form of response against very specific kinds of invaders. Among these kinds of invaders are cancer cells.
The body’s first response to bumps, bruises, cuts, and a broad variety of germ threats are external defenses like skin, hair, tears, and saliva.
Once germ threats enter the body, the internal innate defense system of phagocytes combat the threat. Among phagocytes are white blood cells called neutrophils and eosinophils, both of which initiate inflammation. Inflammation is generally characterized by pain, redness, heat and swelling, as well as occasional loss of function. It serves three main purposes. First, inflammation removes harmful pathogens and cell debris from infected or injured areas. Second, inflammation prevents pathogens and toxins from spreading. And third, inflammation prepares the area for tissue repair.
Also among phagocytes are macrophages. Macrophages may either wander around in the blood or remain fixed in organs such as the liver and the brain, ready to swallow microbes, debris and other foreign invaders. Another type of phagocytes are natural killer cells, residing in the spleen, lymph nodes and red bone marrow. Natural killer cells attack a target threat’s plasma membrane with chemicals called perforins, which cause the target to leak to death. Natural killer cells can also combat foreign microbes by forcing the targets to enter a programmed cell death, known as apoptosis.
When the innate immunity of the body proves insufficient against germ threats, the adaptive defense system identifies the threat and produces specific antibodies and cells as a response. These specialized cells can recognize millions of different pathogens, some not even found in nature, and can distinguish cancerous, foreign or infected cells in an organ from normal cells of the same type.
Its first response is improvised and once it has defeated a threat, the adaptive immunity system stores the information on the threat in a sort of memory, thus allowing it to develop stronger antibodies much faster. This phenomenon is responsible for the body’s full immunity against diseases it has faced before, as is the case in chickenpox and smallpox.
At any point in time, billions of white blood cells are moving through the bloodstream, with about one million white blood cells created every second. These cells constantly seek out the antigen, the foreign body that triggers the generation of antibodies, it could fit for. Once an antibody finds an antigen, the antibody rapidly multiplies in response. Immunity resulting from this kind of response is applied throughout the body, not just at the infected location.
Following Jenner’s smallpox vaccine in 1798, more vaccines have been developed from years of research efforts in immunology.
The first vaccine for cholera, a virulent disease that can kill within hours, was developed in 1917. It is currently being used together with control measures in water and sanitation to prevent outbreaks.
The prototype for a vaccine for polio, an infectious disease characterized by muscle weakness, was first developed in 1948 by Polish immunologist Hilary Koprowski, who used it on himself and his assistant with no recorded side effects. The vaccine for polio currently used worldwide was made by Polish medical researcher Albert Sabin and licensed in 1962.
When an organ malfunctions, it is now common knowledge that another organ from a donor can take its place. However, the immune system may reject the transplanted organ by recognizing it as an unrecognized foreign body, and thus a threat. While rejection cannot be completely prevented, research in immunology has found that some amount of tolerance is possible to minimize rejection. The closer the genetic match a donor and a recipient are, the smaller the chance of rejection. That is why transplants are most commonly performed from one family member to another, most commonly in the case of blood.
Allergic reactions are caused by the immune system’s hypersensitive response to harmless antigens, like dust, pollen, and some types of food. Austrian physician Clemens Baron von Pirquet coined the term in the early 1900s while he was observing patients who had a faster reaction to the second injection of smallpox vaccine compared to the first. Allergy comes from the Greek word allos which means “other”.
Allergic reactions vary from mildly irritating itches to life-threatening inflammation of the respiratory system. Mild allergic reactions may be treated with antihistamine, while life-threatening reactions must be treated immediately with epinephrine. Tests for allergies may be performed on the skin, by either pricking or injecting, or in the blood for more delicate cases. Skin allergy tests have results within minutes or up to 48 hours in some cases. On the other hand, blood allergy tests may take days to complete. Allergy tests for specific drugs may also be performed prior to application, as allergic reactions for drugs may have severe consequences.
Asthma is a chronic disease that makes the airways constantly inflamed. An asthma attack can worsen the inflammation, making breathing difficult. Asthma has a variety of triggers. Most sufferers of asthma are otherwise healthy, but develop symptoms while exercising or performing heavy physical activity. Other asthma triggers include allergies or the inhalation of dust, fumes or gases. An allergist or immunologist is the most qualified physician in diagnosing and treating asthma.
In some people, the immune system may work against the body. It considers the body’s own cells as foreign threats and attacks it as it would any other foreign threat. This condition is called autoimmunity.
One autoimmune disease is Rheumatoid Arthritis, a debilitating disease that begins with an inflammation of the joints in the feet and hands. It then progresses to the wrists, knees, hips and shoulders, causing permanent damage and scarring to joints and cartilage. Scar tissue fuses the bones to the joint, restricting or stopping movement. There is currently no cure for the disease, but anti-inflammatory medication of varying strength helps with pain relief.
Lupus, another autoimmune disease, has symptoms that mimic other diseases. These symptoms include fever, fatigue, joint pain, chest pain, headache, and shortness of breath. In many, but not all, cases, lupus causes a butterfly-shaped rash on the cheeks and the bridge of the nose. Lupus can also cause damage to the kidney, the brain, the lungs, the heart, and several other organs. Like rheumatoid arthritis, there is currently no cure for lupus as well, but medications can help reduce the risk of organ damage.
Immunodeficiency and AIDS
Immunodeficiency is a disorder that occurs when the body’s immune responses are weakened. Immunosuppression is a state that is characterized by immunodeficiency caused by drugs or treatment, such as chemotherapy.
Acquired Immune Deficiency Syndrome (AIDS), on the other hand, specifically targets the body’s immune system and weakens its ability to respond to infection. AIDS is caused by the Human Immunodeficiency Virus (HIV). It is a virus that hijacks the immune system’s cells by replacing the host cell’s DNA with the virus cell’s DNA. From there, the virus replicates itself through the host rapidly and imperfectly, allowing the virus to produce multiple mutations and evolve rapidly. It has spread worldwide and is responsible for millions of deaths, most of which are in sub-Saharan Africa. It is contracted through sexual contact or needle sharing by intravenous drug users. There is no known cure for AIDS, but its symptoms can be managed with an expensive drug cocktail.
9th European Immunology Conference. (n.d.). Retrieved September 11, 2017, from https://immunology.conferenceseries.com/europe/events-list/diagnostic-immunology
Asthma | AAAAI. (n.d.). Retrieved September 11, 2017, from http://www.aaaai.org/conditions-and-treatments/asthma
Become an Immunologist: Education and Career Roadmap. (n.d.). Retrieved September 11, 2017, from http://study.com/articles/Become_an_Immunologist_Education_and_Career_Roadmap.html
Cholera. (n.d.). Retrieved September 11, 2017, from http://www.who.int/mediacentre/factsheets/fs107/en/
Daniels, P. (2007). Body: the complete human. Washington, D.C.: National Geographic.
Greenberg, Steven. A Concise History of Immunology. 1-4
Harper, D. (n.d.). Immune Origin and history of immune by Online Etymology Dictionary. Retrieved September 11, 2017, from
History of Immunology. (n.d.). Retrieved September 11, 2017, from http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/history-immunology
Immunology of Transplant Rejection. (2017, March 09). Retrieved September 11, 2017, from http://emedicine.medscape.com/article/432209-overview#a1
Koch's Postulates to Identify the Causative Agent of an Infectious Disease. (n.d.). Retrieved September 11, 2017, from http://www.life.umd.edu/classroom/bsci424/BSCI223WebSiteFiles/KochsPostulates.htm
Lupus Symptoms. (2014, November 18). Retrieved September 11, 2017, from http://www.mayoclinic.org/diseases-conditions/lupus/basics/symptoms/con-20019676
Norkin, L. (2014, September 30). Thucydides and the Plague of Athens. Retrieved September 11, 2017, from https://norkinvirology.wordpress.com/2014/09/30/thucydides-and-the-plague-of-athens/
Robert Koch - Biographical. (n.d.). Retrieved September 11, 2017, from https://www.nobelprize.org/nobel_prizes/medicine/laureates/1905/koch-bio.html
Science Museum. Brought to Life: Exploring the History of Medicine. (n.d.). Retrieved September 11, 2017, from http://www.sciencemuseum.org.uk/broughttolife/techniques/germtheory
Smallpox: Variolation. (2013, July 30). Retrieved September 11, 2017, from https://www.nlm.nih.gov/exhibition/smallpox/sp_variolation.html
The Editors of Encyclopædia Britannica. (2017, January 06). Élie Metchnikoff. Retrieved September 11, 2017, from https://www.britannica.com/biography/Elie-Metchnikoff
Timeline | History of Vaccines. (n.d.). Retrieved September 11, 2017, from https://www.historyofvaccines.org/timeline?timeline_categories%5B%5D=52
Treating Allergic Reactions to Food. (n.d.). Retrieved September 11, 2017, from https://www.foodallergy.org/life-with-food-allergies/newly-diagnosed/treating-allergic-reactions-to-food
What is an Immunologist? (n.d.). Retrieved September 11, 2017, from http://www.environmentalscience.org/career/immunologist
What is immunology? (n.d.). Retrieved September 11, 2017, from https://www.immunology.org/public-information/what-is-immunology