Master the core vocabulary of the immune system, from innate defenses to allergy and autoimmunity, in clear definitions built for nursing, pre-med and healthcare professionals.
Last updated: November 9, 2026
Immunology explains how the body recognizes and defends itself against microbes, and what happens when that defense fails or turns against the body. This page gathers the essential immunology terms you meet in coursework, charts and lab reports, each defined in one precise sentence.
| Term | Definition |
|---|---|
| Immunity | The body's ability to resist infection and to recognize and eliminate foreign or harmful material. |
| Innate immunity | The rapid, nonspecific first line of defense present from birth, including skin, mucous membranes, phagocytes and inflammation. |
| Adaptive immunity | The specific, slower defense that learns to recognize particular antigens and remembers them for faster responses on later exposure. |
| Antigen | Any molecule, often on a microbe or foreign cell, that the immune system recognizes and that can trigger an immune response. |
| Antibody | A protein made by plasma cells that binds a specific antigen to neutralize it or mark it for destruction; also called an immunoglobulin. |
| Immunoglobulin | The family of antibody proteins, divided into classes such as IgG, IgA, IgM, IgE and IgD according to structure and role. |
| Lymphocyte | A white blood cell central to adaptive immunity, mainly represented by B cells, T cells and natural killer cells. |
| B cell | A lymphocyte that matures into antibody-producing plasma cells and memory cells after meeting its antigen. |
| T cell | A lymphocyte matured in the thymus that coordinates immune responses or directly destroys infected and abnormal cells. |
| Natural killer cell | A lymphocyte of innate immunity that destroys virus-infected cells and some abnormal cells without prior sensitization. |
| Macrophage | A large phagocytic cell that engulfs microbes and debris and presents antigens to T cells. |
| Neutrophil | The most abundant phagocytic white blood cell, which rapidly reaches sites of bacterial infection. |
| Phagocytosis | The process by which a cell engulfs and digests microbes, debris or dead cells. |
| Cytokine | A small signaling protein released by immune cells to regulate inflammation and communication between cells. |
| Complement system | A group of plasma proteins that, once activated in sequence, helps antibodies and phagocytes destroy microbes. |
| Inflammation | A protective tissue response to injury or infection, classically marked by redness, heat, swelling and pain. |
| Lymphoid organ | An organ in which immune cells develop or are activated, such as the thymus, spleen, lymph nodes and bone marrow. |
| Lymph node | A small bean-shaped filter along lymphatic vessels where lymph is screened and immune responses are launched. |
| Thymus | A lymphoid organ in the chest where T cells mature, most active in childhood. |
| Vaccination | The administration of a vaccine to stimulate protective adaptive immunity against a specific disease without causing it. |
| Immunological memory | The ability of the adaptive immune system to respond faster and more strongly on repeated contact with the same antigen. |
| Hypersensitivity | An exaggerated or inappropriate immune reaction to a harmless substance or to the body's own tissues. |
| Allergy | A hypersensitivity reaction to an environmental substance called an allergen, often mediated by IgE antibodies. |
| Anaphylaxis | A severe, rapid, potentially life-threatening systemic allergic reaction affecting several organ systems. |
| Autoimmune disease | A disorder in which the immune system mistakenly attacks the body's own healthy tissues. |
| Immunodeficiency | A state in which part of the immune system is missing or underactive, leading to increased susceptibility to infection. |
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Start learning free →Immunology vocabulary lets you read lab reports, allergy and vaccination records and clinical notes accurately, and explain how the body defends itself. It is core knowledge for nursing school, pre-med and medical assistant training.
Yes. This vocabulary is core to US health programs — nursing school and NCLEX prep, pre-med, and medical assistant training. MediLearn lets you drill these terms with quizzes and flashcards using spaced repetition.
Any molecule, often on a microbe or foreign cell, that the immune system recognizes and that can trigger an immune response.
A small signaling protein released by immune cells to regulate inflammation and communication between cells.
The ability of the adaptive immune system to respond faster and more strongly on repeated contact with the same antigen.