Immunology Vocabulary in English
20 essential immunology words with definitions and example sentences — antibodies, vaccines, and the immune system for B2–C1 ESL learners.
Immunology vocabulary appears throughout science textbooks, news reports about disease outbreaks, and discussions of vaccines and public health. Words such as antibody, antigen, pathogen, and immunity are now part of everyday conversation, especially since the world has paid such close attention to infectious disease. For B2 and C1 learners, mastering these terms makes scientific reading far more accessible.
This page covers 20 key immunology words that describe how the body defends itself against disease. These terms appear in biology courses, medical articles, and reporting on vaccination programmes. You will meet them in academic exams such as IELTS, in popular science writing, and in any serious discussion of how the body fights infection. Many are also useful when talking to doctors and reading health information.
Immunology overlaps closely with several related fields. You may wish to study our Health vocabulary and Medical procedures vocabulary pages alongside this one, as well as the broader Science vocabulary list. Learners interested in how the body works at a deeper level can also explore our Neuroscience vocabulary and Nutrition vocabulary pages. Mastering this immunology vocabulary will strengthen your comprehension of any text about disease, defence, and the human body.
Word List
| Word / Phrase | Meaning | Example Sentence |
|---|---|---|
| antibody | a protein produced by the immune system that recognises and binds to a specific foreign substance in order to neutralise it | After the infection cleared, her blood contained antibodies that could fight the same virus again. |
| antigen | any molecule, often on the surface of a pathogen, that the immune system recognises as foreign and responds to | The vaccine introduces a harmless antigen so the body learns to recognise the real virus. |
| pathogen | a microorganism — such as a bacterium, virus, or fungus — that causes disease | Frequent hand-washing reduces the spread of pathogens between patients. |
| immunity | the body's ability to resist a particular infection, either naturally or after exposure or vaccination | Having recovered from measles as a child, he had lifelong immunity to the disease. |
| vaccine | a preparation that stimulates the immune system to produce protection against a specific disease without causing the illness itself | The new vaccine reduced cases of the disease by more than ninety per cent. |
| lymphocyte | a type of white blood cell central to the immune response, including T cells and B cells | A blood test showed a high lymphocyte count, suggesting the body was fighting an infection. |
| inflammation | the body's protective response to injury or infection, marked by redness, heat, swelling, and pain | The inflammation around the wound was a sign that the immune system was responding. |
| infection | the invasion and multiplication of harmful microorganisms in the body, leading to disease | Doctors prescribed antibiotics to treat the bacterial infection in her lungs. |
| white blood cell | a cell of the immune system that defends the body against infection and foreign material | White blood cells rushed to the site of the cut to destroy invading bacteria. |
| autoimmune | relating to a condition in which the immune system mistakenly attacks the body's own healthy cells | Type 1 diabetes is an autoimmune disease in which the body destroys its own insulin-producing cells. |
| allergen | a normally harmless substance that triggers an exaggerated immune reaction in some people | Pollen is a common allergen that causes sneezing and itchy eyes in spring. |
| antiseptic | a substance that kills or stops the growth of microorganisms on living tissue, used to prevent infection | The nurse cleaned the wound with an antiseptic before applying a dressing. |
| immune response | the coordinated reaction of the immune system to a pathogen or foreign substance | The immune response to the vaccine produced both antibodies and memory cells. |
| T cell | a type of lymphocyte that destroys infected cells directly and helps coordinate the wider immune response | T cells hunt down and kill cells that have been hijacked by a virus. |
| B cell | a type of lymphocyte that produces antibodies against specific antigens | Once activated, B cells release large numbers of antibodies into the bloodstream. |
| histamine | a chemical released by immune cells during an allergic reaction, causing inflammation and other symptoms | Histamine released during hay fever causes the runny nose and watery eyes. |
| phagocyte | a white blood cell that engulfs and digests pathogens and cellular debris | Phagocytes surround invading bacteria and absorb them to clear the infection. |
| tolerance | the immune system's ability to recognise the body's own tissues and not attack them | A breakdown in immune tolerance can lead to autoimmune disease. |
| booster | an additional dose of a vaccine given after the original one to strengthen or renew immunity | She received a booster a year later to keep her immunity at a high level. |
| herd immunity | protection from a disease that occurs when a large proportion of a population is immune, limiting its spread | High vaccination rates created herd immunity that protected even those who could not be vaccinated. |
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Frequently Asked Questions
What is the difference between an antibody and an antigen?
These two words are easy to confuse because they sound similar and work together, but they are opposites in function. An antigen is the foreign substance — usually a molecule on the surface of a pathogen — that the immune system recognises as a threat. An antibody is the protein the body makes in response, which locks onto that specific antigen to neutralise it. A simple memory aid: the antigen is the lock, and the antibody is the key the body builds to fit it. Each antibody is matched to one particular antigen.
What exactly is a pathogen?
A pathogen is any microorganism that can cause disease. The main types are bacteria, viruses, fungi, and parasites. The word comes from Greek roots meaning "disease-producing", which is a useful clue to its meaning. Not all microorganisms are pathogens — many bacteria in the body are harmless or even helpful. In English, you will often see the related adjective pathogenic, meaning capable of causing disease, as in "a pathogenic strain of bacteria". Pathogen is a key word in any text about infection, hygiene, or public health.
What is the difference between a T cell and a B cell?
Both T cells and B cells are types of lymphocyte, a white blood cell at the heart of the immune system, but they do different jobs. B cells produce antibodies — proteins that float through the blood and tag or neutralise invaders. T cells act more directly: some, called killer T cells, destroy the body's own cells once a virus has infected them, while helper T cells coordinate the wider immune response. A simple way to remember it: B cells make the antibodies, while T cells do the targeting and killing.
How do vaccines work?
A vaccine works by teaching the immune system to recognise a pathogen before you ever encounter the real disease. It introduces a harmless antigen — perhaps a weakened or inactivated version of the pathogen, or just a piece of it — which triggers an immune response. The body produces antibodies and memory cells without you becoming ill. Then, if the real pathogen ever appears, the immune system already knows how to destroy it quickly. This is why vaccines build immunity safely, and why some require a booster to keep protection strong over time.
What is herd immunity?
Herd immunity describes the protection a whole population gains when a high enough proportion of people are immune to a disease, either through vaccination or past infection. When most people cannot catch or pass on a pathogen, it struggles to spread, which indirectly protects the vulnerable few who are not immune — such as newborns or people with weakened immune systems. The percentage of the population needed for herd immunity varies by disease: highly contagious diseases like measles require a very high level of immunity to achieve it.
What does "autoimmune" mean?
The prefix auto- means "self", so an autoimmune condition is one in which the immune system mistakenly attacks the body's own healthy cells, treating them as if they were foreign invaders. Normally the immune system shows tolerance towards the body's own tissues, but in autoimmune disease that tolerance breaks down. Well-known examples include type 1 diabetes, rheumatoid arthritis, and multiple sclerosis. The word is a useful one to know because it appears frequently in health articles and medical discussions, and the auto- prefix helps you decode many other English words too.
What do histamine and an allergen do in an allergic reaction?
An allergen is a normally harmless substance — such as pollen, dust, or certain foods — that the immune system wrongly treats as dangerous. When a sensitive person is exposed to an allergen, immune cells release histamine, a chemical that causes the familiar symptoms of an allergic reaction: sneezing, itching, a runny nose, watery eyes, and swelling. This is why allergy medicines are called antihistamines — they block the action of histamine. Understanding both words together makes it much easier to read health advice about hay fever and allergies.
What is the difference between the innate and adaptive immune response?
The immune response has two main branches. The innate immune response is the body's first, fast line of defence — it includes barriers like skin and general-purpose cells such as phagocytes that engulf any invader, plus inflammation. It reacts the same way to every threat. The adaptive immune response is slower but highly specific: it involves lymphocytes — the T cells and B cells — that learn to recognise a particular pathogen and remember it for the future. Vaccines and lasting immunity depend on this adaptive, memory-forming branch.
What is a booster and why is it needed?
A booster is an extra dose of a vaccine given some time after the original course. Immunity from a vaccine can fade over months or years, and a booster "reminds" the immune system, prompting it to produce more antibodies and renew its memory of the pathogen. Some boosters are needed because protection naturally weakens, and others because a pathogen changes over time, as influenza viruses do each year. In English you will often hear phrases like "a booster dose" or "a booster jab", with jab being a common informal British word for an injection.
What is the best way to learn immunology vocabulary?
The most effective approach is to learn the words in connected groups rather than in isolation, because immunology terms work together as a system. Study antigen and antibody as a pair, and T cell and B cell together. Learn the common prefixes and roots — anti- (against), auto- (self), and -phage or phago- (eating) — so you can decode new words. Use the Flash Cards on LexFizz to drill the 20 words on this page, then read short popular-science articles about vaccines and the immune system, where you will see the vocabulary used naturally in context.