Hypersensitivity type 1

Type I Hypersensitivity - an overview ScienceDirect Topic

There are four different types of hypersensitivities, and in the first type or type one, the reactions rely on Immunoglobulin E, or IgE antibody, which is a specific type of antibody - the other major ones being IgG, IgA, IgM, and IgD Clinical Manifestations of Type 1 Hypersensitivity A wide variety of hypersensitivity states can be classified as immediate hypersensitivity reactions. Some have a predominantly cutaneous expression (hives or urticaria), others affects the airways (hay fever, asthma),... The latter are often. Type 3 Hypersensitivity is also known as Hypersensitivity to immune complexes, including: General reaction Skin: Systemic Lupus Erythematosus, Arthus reaction. Kidneys: Lupus Nephritis. Lungs: Aspergillosis. Blood vessels: Polyarteritis. Joints: Rheumatoid Arthritis

Immediate or Type I hypersensitivity is a rapid immunological reaction occurring in a previously sensitized individual that is triggered by the binding of an antigen to IgE antibody on the surface of mast cells Type-I hypersensitivity reaction is an immediate type of reaction mediated by IgE. It is also known as anaphylactic reaction or allergy. It is induced by certain types of antigen called allergens such as pollengrains, dandruff, dusts, food components etc. Allergens induces humoral antibody response by the same mechanism as other soluble.

Type I Hypersensitivity Reaction - StatPearls - NCBI Bookshel

Type I hypersensitivity reaction is commonly called an allergic or immediate hypersensitivity reaction. This reaction is always rapid and can occur within minutes of exposure to an antigen. Type I hypersensitivity reactions are initiated by the interactions between an IgE antibody and a multivalent antigen Type II hypersensitivity • Mediated by abs directed towards antigens present on cell surfaces or the extracellular matrix (type IIA) or abs with agonistic/antagonistic properties (type IIB). • Mechanisms of damage: - Opsonization and complement- and Fc receptor-mediated phagocytosis - Complement- and Fc receptor-mediated inflammatio

Type I hypersensitivity - Wikipedi

Hypersensitivity reactions can be classified into four types. Type I - IgE mediated immediate reaction Type II- Antibody-mediated cytotoxic reaction Type III- Immune complex-mediated reaction Type IV- Cell-mediated, delayed hypersensitivity reaction The first three types are considered immediate hypersensitivity reactions because they occur within 24 hours. The fourth type is considered a delayed hypersensitivity reaction because it usually occurs more than 12 hours after exposure to the allerg TYPE I Hypersensitivity• Type I hypersensitivity - immediateor anaphylactic hypersensitivity• Immediate hypersensitivity is mediated by IgE• The primary cellular component in thishypersensitivity is the mast cell or basophil• The reaction is amplified by neutrophils andeosinophil Type 1 In Type 1 hypersensitivity reactions mast-cell activation is induced by secretion of IgE antibodies. Initial exposure to the antigen causes the priming of Th2 cells, and their release of IL-4 causes the B cells to switch their production of IgM to IgE antibodies which are antigen-specific Hypersensitivity Type 1 Reactions Made Easy- Type 1 Allergic ReactionFlashcards and other COOL STUFF : https://www.patreon.com/medsimplfiedMerch STORE : bit...

Type I hypersensitivity Osmosi

Osmosis presents this thorough and easy-to-follow guide to Type 1 Hypersensitivity. Learn about the clinical presentation, from prevention to diagnosis to tr.. Type 1 hypersensitivity reactions usually have an early and a late phase. Hypersensitivity and anaphylaxis The possibility of cross-reactivity between a type 1 hypersensitivity reaction (e.g., nasal allergy) and a type 4 hypersensitivity reaction (essentially cell-mediated immunoactivity) has been postulated Figure 1 Induction and effector mechanisms in type 1 hypersensitivity: Hypersensitivity refers to excessive, undesirable (damaging, discomfort-producing and sometimes fatal) reactions produced by the normal immune system. Hypersensitivity reactions require a pre-sensitized (immune) state of the host

Type-1 or anaphylactic hypersensitivity Type-II or cytotoxic hypersensitivity Type-III or immune complex hypersensitivity Type-IV or Delayed or Cell mediated hypersensitivity Type-V or Stimulatory hypersensitivity (Later added) 8 1/1/2014 Prof. Muhammad Akram Hossain, Hypersensitivity-1 Type I (IgE-mediated or anaphylactic-type) is the most common type of hypersensitivity, seen in about 20% of the population. IgE is made in response to an allergen (Figure 1 and Figure \(\PageIndex{2}\)). In allergic individuals, the levels of IgE may be thousands of times higher than in those without allergies

Type 1 (Anaphylactic) Hypersensitivity Reaction Microbe

  1. utes from the time of exposure to the antigen, although sometimes it may have a delayed onset (10 - 12 hours).In type 1 hypersensitivity, an antigen is presented to CD4+ Th2 cells specific to the antigen that stimulate B cell production of IgE antibodies also specific to the antigen
  2. Type 1 diabetes (T1DM) is an auto-immune disease commonly associated with other autoimmune conditions. The generation of antibodies to insulin can occur, but is rarely clinically significant. Generation of IgE anti-insulin antibodies can lead to Type 1 allergic reactions associated with urticaria, angioedema, bronchospasm and hypotension
  3. utes after the interaction of antigen with IgE antibody bound to the surface of mast cells (sensitized mast cells). The reaction is initiated by entry of an antigen, which is called an allergen because it triggers allergy
  4. Cytokine exposure causes a reaction similar to a type 1 hypersensitivity reaction and may be clinically indistinguishable: the symptoms appear within the first few hours and are mild to moderate. Diagnose, assess, and manage infusion reactions: as seen in the Clinical Journal of Oncology Nursing
  5. Summary Type I Hypersensitivity Reactions (T1HSR) are a type of unwanted immune response, caused by pre-formed IgE antibodies against harmless allergens. T1HSR is more commonly known as allergy. Because it is caused by pre-formed antibodies, type 1 hypersensitivity reactions happen quickly, almost instantaneously after exposure. The resulting immune response is divided into two phases, the.

Later in 1963, Coombs and Gell described a classification of allergic reactions which may be deleterious to the tissues and harmful to the host 1 . According to Gell and Coombs classification, hypersensitivity is of four different types: I, II, III and IV. Type I, II, and III are antibody-mediated whereas type IV is mediated by T cells 1. Type I Hypersensitivity (Anaphylaxis): This type of hypersensitivity is the most common among all the types. About 17% of the human population may be affected, probably due to a natural proneness controlled by the genetic make-up. Anaphylaxis which literally means opposite of protection — is mediated by IgE antibodies through. Hypersensitivity Type 1. STUDY. Flashcards. Learn. Write. Spell. Test. PLAY. Match. Gravity. Created by. mike_ganzhorn. Terms in this set (32) Four types of hypersensitivity. Sensitization and production of IgE - 3 types of cells and locations: Mast cells found in mucosal and epithelial tissues lining body surface Type IV hypersensitivity is often called delayed type hypersensitivity as the reaction takes several days to develop. Unlike the other types, it is not antibody-mediated but rather is a type of cell-mediated response. This response involves the interaction of T-cells, monocytes, and macrophages

Hypersensitivity: Type 1, 2, 3 and 4, Causes and

Multiple Choice Questions on Hypersensitivity Reactions. 1. Allergy to penicillin is an example of. 2. Type IV hypersensitivity is also called as. 3. The most common class of antibody involved in type II hypersensitivity is. 5. Type III hypersensitivity is triggered by Patofysiologi. Ved type 1 hypersensitivitet vert eit antigen presentert for CD4+ Th2-celler som er spesfikke for antigenet, og som stimulerar B-celleproduksjon av IgE-antistoff som òg er spesifikke for antigenet.Forskjellen mellom ein normal infeksiøs immunrespons og ein type 1 hypersensitivitetsrespons, er at det involverte antistoffet er IgE i staden for IgA, IgG eller IgM Four types of immune responses are usually described, but the main reaction involving the eyes is type 1. They are also called allergic reactions types 1-4. type 1 hypersensitivity An immediate, abnormal reaction occurring when an antigen reacts with an antibody (e.g. immunoglobulin E (IgE)) attached to a mast cell or basophil. This leads to. Type II hypersensitivity can lead to tissue damage by three main mechanisms: (1) direct cellular destruction (e.g., autoimmune hemolytic anemia and immune thrombocytopenia), (2) inflammation (e.g., Goodpasture's syndrome and acute rheumatic fever), and (3) disrupting cellular function (e.g., myasthenia gravis and Graves' disease)

77P - Antibody-Mediated Diseases, Type II Hypersensitivity

This is basically typed I Hypersensitivity reaction or Anaphylactic reaction. So every technician should know how to deal with such a situation. Causes: An anaphylactic reaction may be due to: Penicillin. Stings. Food like nuts, eggs, milk, and fish. Sign and symptoms of Type I hypersensitivity reaction: The type 1 reaction may be Type I hypersensitivity reactions involve the activation of tissue mast cells and blood basophils when IgE molecules bound to their surface become linked together by an allergen. Substantial numbers of individuals develop allergies due to type I (IgE‐mediated) hypersensitivity, also referred to as atopic allergy The cellular effects of Type 1 hypersensitivity reaction. 4. Manifestations of early and late phases of type 1 hypersensitivity reaction. 5. Anaphylactic shock. 6. The role of histamines, bradykinin, cytokines and different immune modulators. 7. The mechanism and site of actions of different treatment options available

Type III hypersensitivity diseases are due to antibody-antigen complexes that circulate and then deposit in tissues. Finally, type IV hypersensitivity diseases are not caused by antibody but caused by T cells that can target their antigen wherever it's located Type 1 hypersensitivity. This type of hypersensitivity reaction is also called immediate hypersensitivity because it occurs very quickly (within minutes). It is the type of reaction that occurs in hay fever, seasonal rhinitis, asthma or even anaphylaxis TX for Type 1 Hypersensitivity. Environmental measures, pharmacologic intervention: antihistamines, adrenergic agents, phosphodiesterase inhibitors, cromolyn sodium and nedocromil sodium, corticosteroids, leukotriene receptor antagonists, leukotriene formation inhibitors, allergen immunotherapy

Type 3 Hypersensitivity (Type III) - YouTube

Hypersensitivity type 1 January 10, 2017 Off All, Discussion (50%) This should discuss the significance of the results. What were the experiments trying to show? You will need to consider what mast cells do and suggest which molecule is responsible for the effect on ileal contraction. The discussion section should also mention the different. Hypersensitivity Type 3; Hypersensitivity Type 4; Hypersensitivity Type-1. Anaphylactic; IgE or reagin dependent. Antibodies, cytotropic IgE antibodies are fixed on the surface of tissue cells (basophils and mast cell) in sensitized individual. Clinical complex of Type 1 reaction includes potential system and anaphylaxis and localized responses. This type of hypersensitivity comes from a cell-mediated response instead of from antibodies like in the other types. In particular, the T-lymphocytes, a type of white blood cell in the body, have something to do with the development of the condition, so it's also called cell-mediated hypersensitivity

Type I Hypersensitivity Reaction - SlideShar

the terms Type I and Type IV are used routinely (Figure-1). Type I or immediate hypersensitivity is characterized by the production of IgE antibodies against foreign proteins that commonly present in the environment, for example pollens, animal dander or dust mites. These antibodies bind specifically to a high-affinity recepto Type I hypersensitivity reactions are usually rapid and occur within just a few minutes, because of this they are often referred to as immediate hypersensitivity. In Chafin's comic he describes what is happening to the immune system when exposed to the specific type 1 allergen, pollen Type 1 hypersensitivity reactions are immunoglobulin E (IgE)-mediated, occur rapidly within minutes or hours, and can result in anaphylaxis or angioedema. Delayed-type hypersensitivity to HA filler are rare reactions, occurring anywhere between 24 hours to weeks or months after placement The first three types are antibody-mediated and the fourth type is mediated mainly by T-cell and macro-phases i.e. cell-mediated (Table 11.1 and 11.2; Fig. 11.2). 1. Type I Hypersensitivity: Type I hypersensitive reactions are the com­monest type among all types which is mainly induced by certain type of antigens i.e. allergens 1 Hypersensitivity Robert Beatty MCB150 Type I IgE Mediated Classic Allergy Type II IgG/IgM Mediated rbc lysis Type III IgG Mediated Immune complex Disease Type IV T cell Delayed Type Hypersensitivity Gel and Coombs classification of hypersensitivities. TYPE I Hypersensitivity Classic allergy Mediated by IgE attached to Mast cells

Type 1: Allergies. The first type of hypersensitivity - and probably the one most people have experienced - is any sort of allergy. Allergies are quite common in the United States and around the world, affecting roughly one in three people at some point in their lives. There are many different causes of allergies, ranging from certain foods. Type I Hypersensitivity Allergy. Immunopathology. Type 1 Anaphylactic Hypersensitivity Reaction. 26 Type 1 Hypersensitivity At Acadia University Studyblue. Hypersensitivity Reactions. Type I Hypersensitivity Reaction Mechanism And Clinical. 21 6 Diseases Associated With Depressed Or Overactive Immune Type II Hypersensitivity. 28 Type III (Immune Complex) Hypersensitivity. 29 • Another attempt at protection gone wrong: • IV infusion anti-toxin antiserum • Followed with SQ injection of small dose of toxin • Outcome: local (cutaneous) erythema, swelling hemorrhage and necrosis within Types: Hypersensitivity reactions are classified into four types. Hypersensitivity classification [1] [2] Summary of pathophysiology Examples; Type I: immediate: Preformed IgE antibodies coating mast cells and basophils are crosslinked by contact with free antigen

A hypersensitivity reaction is an inappropriate or exaggerated response to an antigen or an allergen. The traditional classification for hypersensitivity reactions is that of Gell and Coombs and is currently the most commonly known classification system. It divides the hypersensitivity reactions into the following 4 types Immunology Quiz on Hypersensitivity Reactions. This immunology quiz is designed to assess your knowledge in ' Hypersentivity '. Choose the best answer from the four options given. When you've finished answering as many of the questions as you can, scroll down to the bottom of the page and check your answers by clicking 'Score'

Type I hypersensitivity reaction: mechanism and clinical

This page includes the following topics and synonyms: Hypersensitivity Reaction, Hypersensitivity, Gell and Coombs Classification, Coombs and Gell Classification, Type 1 Hypersensitivity, Immediate Hypersensitivity Reaction, Type 2 Hypersensitivity, Cytotoxic Antibody Reaction, Type 3 Hypersensitivity, Immune Complex Reaction, Type 4 Hypersensitivity, Delayed-Type Hypersensitivity, Stimulatory. The big example (obviously) of this type of hypersensitivity is allergy. Pollen, cat dander, peanuts - they all have the same mechanism and this is it. Type II (antibody-mediated) hypersensitivity There are a ton of diseases that have an underlying type II hypersensitivity reaction going on. Here's a partial list: 1 Earn 1 Contact Hour - Free of Charge The goal of this CE activity is to provide nurses and nurse practitioners with knowledge and skills to recognize and manage acute hypersensitivity reactions (HSRs) occurring as a result of medication administration. After reading this article, you will be able to: Recognize early signs and symptoms o


Hypersensitivity disorders often involve more than 1 type. Type I Antigen binds to IgE that is bound to tissue mast cells and blood basophils, triggering release of preformed mediators (eg, histamine, proteases, chemotactic factors) and synthesis of other mediators (eg, prostaglandins, leukotrienes, platelet-activating factor, cytokines) Three variants of Type IV hypersensitivity reaction are recognized (Figure-1). Contact hypersensitivity and tuberculin type hypersensitivity both occur within 72 hours of antigen challenge. Granulomatous hypersensitivity reactions develop over a period of 21-28 days; the granulomas are formed by the aggregation and proliferation of macrophages Hypersensitivity case studies with information on patient presentation, differential diagnosis, immunology discussion and evaluation on your understandin Type 1 diabetes is a disease commonly managed by internists, the cornerstone of which is insulin therapy. Though relatively uncommon, hypersensitivity reactions to insulin make disease management significantly more challenging and place the patient at risk for diabetic ketoacidosis (DKA)

Type I, or immediate hypersensitivity, encompasses IgE-mediated responses to foreign antigens. These reactions may be minor and local or may be severe and generalized. In its most extreme form, type 1 hypersensitivity or allergy is expressed as a lethal shock syndrome called anaphylaxis. Anaphylaxis is an acute systemic manifestation of the. In this chapter, the features of type I hypersensitivity reactions and the major components involved as well as their potential roles in the induction and regulation of allergic responses are discussed. A half century ago, Gell and Coombs classified the hypersensitivity reactions into four types based on the immunologic mechanisms related to. Type II hypersensitivity reactions involve IgG and IgM antibodies directed against cellular antigens, leading to cell damage mediated by other immune system effectors. Type III hypersensitivity reactions involve the interactions of IgG, IgM, and, occasionally, IgA 1 antibodies with antigen to form immune complexes. Accumulation of immune. Type IV. E. This isn't a hypersensitivity reaction. Question 6 Explanation: These are symptoms of hypersensitivity caused by an allergen, in this case, animal dander. These types of allergic reactions are type I reactions. Type I reactions tend to occur very soon after exposure to the allergen. Question 7 Immunology: MCQ on Immediate and Delayed Hypersensitivity. 1) Hypersensitivity reactions are broadly classified into four different types. Which of the following hypersensitivity occurs via IgE antibody? 2) The T helper 1 cells release cytokines to activate macrophage or T cells and cause direct cellular damage

  1. Some examples of type 1 hypersensitivity: Allergic asthma. Allergic conjunctivitis. Allergic rhinitis (hay fever) Anaphylaxis. Which abnormality is an example of a type 4 delayed hypersensitivity reaction? Contact allergy is a delayed type of hypersensitivity (type IV) that requires weeks to months of allergen exposure for sensitization.
  2. utes of exposure to it. The primary class.
  3. utes after the combination of an antigen with antibody bound to mast cells in individuals previously sensitized to the antigen. These reactions are often called allergy and the antigens are called allergens.

Chapter 11: Hypersensitivity Reactions, Type 1

Figure 1. Illustration of Type I hypersensitivity reaction. IgE is the main mediator of Type I hypersensitivity or anaphylactic reaction. The main biological function of this immunoglobulin molecule in anaphylactic reaction is to cross-link (i.e., act as a bridge) between the allergen that invaded the body and the mast cells or basophils which are known to contain cytoplasmic granules (e.g. There are 4 types of hypersensitivity reactions: Type I hypersensitivity reactions (immediate hypersensitivity reaction) is an antibody mediated reaction. The initial contact with the antigen (allergen) results in memory formation, this is IgE based. A reaction is caused by the interaction between IgE antibodies and multivalent antigens TYPE IV Hypersensitivity. This is mediated by T-cells. There are 2 types that involve CD4/8+T Cells. A) Acute (within 2-3 days) Tuberculin test, contact dermatitis: mediated by CD4+ T helper cells cd4+ cells recognize ag (tuberculin), this leads to the formation of sensitized cd4+ cells

Allergy and Hypersensitivity

Type I Hypersensitivity Reaction Concise Medical Knowledg

  1. Early and Late Phases in Type I Hypersensitivity. 1. Early Phase. The metachromatic cytoplasmic granules of basophils and mast cells contain a variety of preformed mediators (Table 21.3). After cross-linking of Fc-receptor associated IgE, mast cells and basophils undergo a series of biochemical and structural changes
  2. hypersensitivity: types, symptoms, treatment Hypersensitivity refers to extreme physical sensitivity to particular substances or conditions. It is the undesirable reactions produce by the normal immune system in the form of allergie
  3. Hypersensitivity may be caused by prescription medication, and changing to another drug could help. Allergies are normally classified as Type 1 hypersensitivity. These involve allergic reactions that produce an almost immediate effect. The individual may begin to have difficulty breathing, experiencing what amounts to an asthma attack
  4. ation or removal of antigens from host body by means of effector molecules. The effectors molecules generally induce local inflammatory response and removes antigen without extensively damaging host tissues. However in.
  5. Type I hypersensitivity reactions are a form of acute inflammation that results from the interaction of antigens with mast cell-bound IgE. This leads to the release of mast cell granule contents (Figure 28-1). The granule contents in turn cause acute inflammation. The benefits of this type of inflammation are unclear, but it is of major.
Management of Nonsteroidal Anti-inflammatory Drug-Induced

The granules released into the interstitium constitute the fuel for hypersensitivity reactions and can be generalized into two types. Immediate phase hypersensitivity is mediated by proteins and amines (Eg histamine) and results in the classic wheal and flare reaction in minutes after exposure. Late phase hypersensitivity is mediated by. Allergies Type 1 Hypersensitivity TechZarii May 15, 2021 . Allergies Type 1 Hypersensitivity. allergies occur as a result of hypersensitivity of the system to substances in the surroundings that are commonly harmless there are four wholly differing types of hypersensitivity kinds one two three our supermolecule mediate antibodies collectively. Type II hypersensitivity reactions involve IgG and IgM antibodies directed against cellular antigens, leading to cell damage mediated by other immune system effectors. Type III hypersensitivity reactions involve the interactions of IgG, IgM, and, occasionally, IgA [1] antibodies with antigen to form immune complexes. Accumulation of immune. Type 1 hypersensitivity reactions may be accompanied by an increase in eosinophils, as noted with differential count of peripheral white blood cells. The serum tryptase may be increased in the hour following mast cell activation Fig. 23.1 The Coombs and Gell classification of the four types of hypersensitivity reaction. In type I hypersensitivity, mast cells bind IgE via their Fc receptors. On encountering allergen the IgE becomes cross-linked, inducing degranulation and release of mediators that produce allergic reactions

AllergyCase Report of Subcutaneous Nodules and Sterile AbscessesAcute Interstitial Nephritis: Immunologic and Clinical

Type 1, 2, 3 & 4 Hypersensitivity Stomp On Step

  1. Type B reactions — Type B reactions represent hypersensitivity reactions. They make up 10 to 15 percent of adverse drug reactions, occur in a susceptible subgroup of patients, and have signs and symptoms that are different from the pharmacologic actions of the drug. The great majority of hypersensitivity reactions are mediated by immunologic.
  2. Question 1. 1. Which of the following are examples of type III hypersensitivity: Answers: Myasthenia Gravis and Graves' Disease. Allergies and Asthma. Rheumatoid Arthritis and Arthus reaction.
  3. Synonyms for Type 1 hypersensitivity in Free Thesaurus. Antonyms for Type 1 hypersensitivity. 22 synonyms for allergy: sensitivity, reaction, susceptibility, antipathy, hypersensitivity, sensitiveness, dislike of, hatred of, hostility to or towards.... What are synonyms for Type 1 hypersensitivity
  4. Allergies: Hypersensitivity Type 1. Home / General / Allergies: Hypersensitivity Type 1. Health Expert. General | Allergic reactions occur when an individual who has produced IgE antibody in response to an innocuous antigen, or allergen, subsequently encounters the same allergen. The allergen triggers the activation of IgE-binding mast cells in.
  5. Thus, Type 1 Hypersensitivity would account for the various symptoms observed in a person sensitized to dog allergens. However, humans can experience allergic reactions/conditions associated with other types of hypersensitivity e.g. Type 2 Hypersensitivity and autoimmune haemolytic, but these are not relevant in the context of people allergic.

Hypersensitivity- Introduction, Causes, Mechanism and Type

  1. g mast cells
  2. istered to a patient with type B blood. The anti-A isohemagglutinin IgM antibodies in the recipient bind to and agglutinate the inco
  3. IgE Mediated (Type 1) Hypersensitivity. How do allergies develop? Allergies are exaggerated and inappropriate immune responses caused by B cells producing excess IgE antibodies. An allergen is a foreign substance, often food, pollen, dust (small fragments of organic material), or a chemical such as an antibiotic. The allergen binds to the.
  4. utes of exposure to the allergen. While the late-phase may develop 4 to 12 hours post early phase reaction and can last for up to 24 to 73 hours
  5. istration of etoposide is an unusual event impacting less than 1% of patients. The etiology is unknown, although it is speculated that patients are reacting to the polysorbate 80 used to dissolve etoposide
  6. Drug hypersensitivity results from interactions between a pharmacologic agent and the human immune system. These types of reactions constitute only a small subset of all adverse drug reactions

Hypersensitivity to platinum compounds typically develops after multiple cycles of therapy, suggesting that it is an acquired, anaphylactic reaction consistent with type 1 hypersensitivity. In contrast, reactions to taxanes and monoclonal antibodies are immediate, often occurring within the first few minutes of the first infusion, which. Types of Hypersensitivity Reactions. The four types of hypersensitivity reaction (I to IV) are defined by the principal mechanism responsible for a specific cell or tissue injury that occurs during an immune response . Types I, II, and III reactions are antibody dependent and type IV is cell mediated Type IV Hypersensitivity Reaction. Type IV hypersensitivity reaction, or delayed-type hypersensitivity, is a cell-mediated response to antigen exposure. The reaction involves T cells, not antibodies, and develops over several days. Presensitized T cells initiate the immune defense, leading to tissue damage