13.6.2. Hypersensitivity

Hypersensitivity. Allergies

The function of the immune system is to destroy foreign antigens without causing any harm to the person, but, on occasions, these responses can be of excessive force in the face of harmless or not very dangerous molecules, and can produce serious effects on people, even death.

Two types of hypersensitivity are distinguished:

Immediate or anaphylactic hypersensitivity: allergy

The allergy is a hypersensitivity mechanism or exaggerated immune response to the presence of antigens safe or very dangerous.

The immediate or anaphylactic hypersensitivity develops rapidly, about 10 to 20 minutes after exposure to the antigen, which in this case is called allergen.

An allergen is a substance that induces a hypersensitivity (allergic) reaction in susceptible people who have previously been in contact with them. Some of the most common allergens are bee venom, pollen proteins, animal hair, dust mite feces, some medications like penicillin, some foods like shellfish, peanuts, etc.

Development of the allergic reaction

The allergic reaction develops following these phases:

1.- Allergen uptake by antigen presenting cells.

2.- Sensitization to the allergen.

When the first contact with the allergen occurs, no external symptoms are shown, but the immune system recognizes the allergen since the antigen-presenting cells (APCs) phagocytize it and show its fragments in the MHC-II to the helper T lymphocytes (T_H), which recognize and activate neighboring B lymphocytes. The B lymphocytes into plasma cells and release large amounts of IgE immunoglobulins which bind to the constant region of basophils blood and mast cells tissues. This is the process of awareness raising.

3.- Release of the content of the histamine-filled mast cell granules.

When the second contact with the allergen occurs, the allergic reaction occurs. The allergen binds to the IgE that coat mast cells and basophils, causing their degranulation, expelling substances from the cell cytoplasm. These secreted substances cause inflammation (histamines, prostaglandins, serotonin, etc.) and allergy discomfort, such as dermatitis or diarrhea, if it is a food allergy, mucus secretion if it is an allergy caused by substances contained in the air, etc. If mast cells and basophils discharge histamineblood, dilation will causes blood vessels, leading to a generalized reaction, with the contraction of the bronchioles and generally vasodilation can cause death by asphyxiation or a significant decrease in the blood pressure (anaphylactic shock).

Delayed hypersensitivity

It can also happen that the reaction occurs later, even several weeks after contact with the antigen, as in delayed hypersensitivity.

Antibodies are not involved in delayed hypersensitivity, but rather a type of T lymphocytes that, after a second contact with the same antigen, release substances that stimulate the action of macrophages and trigger an inflammatory process.

An example of this type of hypersensitivity is the cause of contact dermatitis caused by some cosmetics, clothing, jewelry or plants in contact with the skin, whose proteins bind with haptens present in these products and originate the antigens that trigger the disease. reaction. Since the symptoms (itching, rash, ...) are similar to those of anaphylactic hypersensitivity, these reactions are incorrectly called contact allergies.

Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU)

Aragon, September 2019, option B, question 5.

Answer the following questions: (1 point)

a) Define: autoimmune disease and allergic (or hypersensitivity) reaction. (0.5 points)

b) Define passive natural immunity and give an example. (0.5 points)

Aragon, June 2018, option B, question 1.

Genetics and environmental factors play an important role in the origin of allergies. (1 point)

a) What do we call an allergy? (0.5 points)

b) What does the allergic response produce? (0.25 points)

c) What is the nature of antigens and antibodies? (0.25 points)

Aragon. June 2017, option A, question 5.

Define the following concepts related to the immune system: hypersensitivity. (0.2 points)

Aragon. September 2015, option B, question 5.

Define the following statements: (2 points)

Hypersensitivity reaction. (0.5 points)

Aragon. September 2014, option B, question 4 .

Define the following terms referring to immunity: (2 points)

Allergic or hypersensitivity reaction. (0.5 points)

Andalusia, September 2014, option A, question 5.

Pollen is a foreign body for the body that, in allergy sufferers, causes annoying reactions (cough, sneeze, itching, nasal congestion).

Why a first contact with pollen in these people may not cause external symptoms, which do appear after a second exposure? [0.5].

Does this mean that those allergic to pollen are immunodeficient? [0.5]. Reason for the answers.

Basque Country, July 2020, option 3A

It is estimated that in developed countries a high percentage of the population suffers from some type of allergy.

a) (1 point) Indicate what an allergen is. Give some examples of allergens. Give reasons for your answer.

b) (1 point) What type of immune system reaction occurs in an allergy? In this situation, what three basic processes can be triggered?

c) (0.5 points) Mention one type of cell and one type of molecule involved in allergic processes.

Madrid, July 2021, question A5

In relation to the immune response:

Peanuts are one of the most common causes of food allergies. The hypersensitivity reaction appears within a few minutes of ingestion of this dried fruit.

a) What is a hypersensitivity reaction? What is the difference between antigen and allergen? (1 point).
b) Describe the processes that occur during an immediate hypersensitivity reaction using the following terms in the proper order: mast cell, allergen, histamine, IgE (1 point).

Galicia, July 2021, question 8d

Briefly: what are hypersensitivity and autoimmunity?

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Skip navigation Biology 2nd Baccalaureate Biology 2nd Bac. 1. Bioelements and biomolecules. Water and mineral salts 1.1. Chemical bonds in biology 1.1.1. Intramolecular bonds 1.1.1.1. Covalent bond 1.1.1.2. Ionic bond 1.1.2. Intermolecular bonds 1.1.2.1. Van der Waals forces 1.1.2.2. Hydrogen bonds 1.2. The chemical basis of life: inorganic and organic components 1.2.1. Primary bioelements 1.2.2. Secondary bioelements 1.2.3. Trace elements 1.3. The immediate principles or biomolecules 1.3.1. Water 1.3.1.1. Chemical structure of water 1.3.1.2. Properties and functions of water 1.3.2. Mineral salts 1.3.2.1. Functions of salts in solution 1.3.2.2. Colloidal solutions and dispersions 1.3.2.3. Properties of colloidal dispersions 1.3.2.4. Diffusion, osmosis and dialysis 1.3.2.4.1. Diffusion 1.3.2.4.2. Osmosis 1.3.2.4.3. Dialysis 1.4. Bibliography 2. Glucides 2.1. Glucid concept 2.2. Classification of carbohydrates 2.3. Monosaccharides 2.3.1. Trioses 2.3.1.1. Spatial isomerism or stereoisomerism 2.3.2. Tetroses 2.3.3. Pentoses 2.3.3.1. Monosaccharide cyclization 2.3.4. Hexoses 2.4. The N-glucosidic and O-glucosidic bonds 2.4.1. Substances derived from monosaccharides 2.5. Disaccharides 2.6. Polysaccharides 2.6.1. Homopolysaccharides 2.6.1.1. Reserve homopolysaccharides 2.6.1.2. Structural homopolysaccharides 2.6.2. Heteropolysaccharides 2.6.3. Heterosides 2.7. General functions of glucides 2.8. Bibliography 3. Lipids 3.1. Lipid concept 3.2. Classification of lipids 3.2.1. Fatty acids 3.2.1.1. Saturated and unsaturated fatty acids 3.2.1.2. Chemical properties of fatty acids 3.2.1.3. Physical properties of fatty acids 3.2.1.4. Fatty Acid Functions 3.2.2. Saponifiable lipids or with fatty acids 3.2.2.1. Simple lipids 3.2.2.1.1. Acylglycerides 3.2.2.1.2. Cerides 3.2.2.2. Complex lipids 3.2.2.2.1. Phospholipids 3.2.2.2.2. Glycolipids 3.2.3. Unsaponifiable lipids or without fatty acids 3.3. Lipid functions 3.4. Bibliography 4. Proteins 4.1. Introduction to proteins 4.2. Amino acids 4.2.1. Classification of amino acids 4.2.2. Properties of amino acids 4.3. The peptide bond 4.4. Protein 4.4.1. Protein structure 4.4.1.1. Primary structure of proteins 4.4.1.2. Secondary structure of proteins 4.4.1.3. Tertiary structure of proteins 4.4.1.4. Quaternary structure of proteins 4.4.2. Protein properties 4.4.3. Classification of proteins 4.4.3.1. Holoproteins 4.4.3.2. Heteroproteins 4.4.4. Protein functions 4.5. Enzymes 4.5.1. Structure of enzymes 4.5.2. The active center of enzymes 4.5.3. General Mechanism of Enzyme Catalysis 4.5.4. Regulation of enzyme activity 4.5.5. Allosteric enzymes 4.5.6. Nomenclature and classification of enzymes 4.6. The vitamins 4.6.1. Fat-soluble vitamins 4.6.2. Water soluble vitamins 4.7. Bibliography 5. Nucleotides and nucleic acids 5.1. The chemical composition of nucleic acids 5.1.1. Components of nucleic acids 5.1.2. Concept, types and functions of nucleic acids 5.1.3. Nucleosides 5.1.4. Nucleotides 5.1.4.1. Nucleotide functions 5.1.5. Nucleic acids 5.2. Deoxyribonucleic acid (DNA) 5.2.1. DNA structure 5.2.1.1. Primary structure of DNA 5.2.1.2. Secondary structure of DNA 5.2.1.3. Tertiary structure of DNA 5.2.1.3.1. Tertiary structure of DNA in prokaryotes 5.2.1.3.2. Tertiary structure of DNA in eukaryotes 5.2.1.4. Quaternary structure of DNA 5.2.2. DNA types 5.2.3. Genetic material: chromatin and chromosomes 5.2.3.1. Karyotype and karyogram 5.3. Ribonucleic acid (RNA) 5.3.1. RNA types 5.3.1.1. Transfer RNA 5.3.1.2. Messenger RNA 5.3.1.3. Ribosomal RNA 5.3.1.4. Nucleolar RNA 5.3.1.5. Small nuclear RNA 5.3.2. Functions of ribonucleic acids 5.4. Bibliography 6. Cell morphology 6.1. Cell concept 6.1.1. Cell history 6.1.2. Cell theory 6.2. Levels of cellular organization 6.2.1. General characteristics of cells 6.2.2. Prokaryotic cells 6.2.2.1. Prokaryotic cell morphology 6.2.2.2. Structure of prokaryotes 6.2.2.2.1. Bacterial capsule 6.2.2.2.2. Bacterial wall 6.2.2.2.3. Plasma membrane 6.2.2.2.4. Cytoplasm-Ribosomes-Inclusions 6.2.2.2.5. Bacterial DNA 6.2.2.2.6. Bacterial appendages 6.2.2.3. Bacteria Physiology 6.2.3. Eukaryotic cells 6.2.3.1. Animal and plant cell 6.2.3.1.1. Animal eukaryotic cell 6.2.3.1.2. Plant eukaryotic cell 6.2.3.2. Cell Evolution: Endosymbiont Theory 6.3. Size, shape and quantity 6.4. The plasma membrane 6.4.1. Chemical composition of the membrane 6.4.2. The structure of the membrane. The fluid mosaic model 6.4.3. Functions of the plasma membrane 6.4.4. Transport across the membrane 6.4.4.1. Small molecule transport 6.4.4.2. Macromolecule transport 6.4.5. Plasma membrane differentiations 6.5. The cell wall of plant cells 6.5.1. Chemical composition of the cell wall 6.5.2. Cell wall structure 6.5.3. Cell wall differentiations 6.5.4. Cell wall functions 6.6. Extracellular matrix or glucocalyx 6.7. Cytosol or hyaloplasm 6.8. The cytoskeleton 6.8.1. Microfilaments or actin filaments 6.8.2. Intermediate filaments 6.8.3. Microtubules 6.9. Cell membrane and organelle systems 6.9.1. Membrane systems 6.9.1.1. The endoplasmic reticulum 6.9.1.2. Golgi apparatus 6.9.2. Cell organelles 6.9.2.1. Lysosomes 6.9.2.2. Peroxisomes 6.9.2.3. Vacuoles 6.9.2.4. Mitochondria 6.9.2.4.1. Functions of the mitochondria 6.9.2.5. Plastids 6.9.2.5.1. Chloroplasts 6.9.2.6. Ribosomes 6.9.2.7. Centrosome 6.9.2.8. Cilia and flagella 6.10. Cell motility 6.11. The cell nucleus 6.11.1. Characteristics of the cell nucleus 6.11.2. The interphase nucleus 6.11.3. The mitotic nucleus or nucleus in division 6.12. Bibliography 7. Metabolism 7.1. Metabolism 7.1.1. Energetic Aspects of Cellular Chemical Reactions 7.2. Catabolism 7.2.1. Catabolism and obtaining energy 7.2.2. Carbohydrate catabolism 7.2.2.1. Glycolysis 7.2.2.2. Cellular respiration 7.2.2.2.1. Oxidative decarboxylation 7.2.2.2.2. Krebs cycle 7.2.2.2.3. Electron transport chain 7.2.2.2.4. Energy balance of cellular respiration 7.2.2.3. Fermentations 7.2.2.3.1. Alcoholic or ethyl fermentation 7.2.2.3.2. Lactic fermentation 7.2.2.3.3. Other types of fermentations 7.3. Anabolism 7.3.1. Autotrophic anabolism 7.3.2. Photosynthesis 7.3.2.1. Photochemical or light phase 7.3.2.1.1. Photosystems 7.3.2.1.2. Photophosphorylation 7.3.2.1.2.1. Non cyclic photophosphorylation 7.3.2.1.2.2. Cyclic photophosphorylation 7.3.2.2. Biosynthetic or dark phase 7.3.2.3. Factors influencing photosynthesis 7.3.2.4. Products of photosynthesis 7.3.3. Chemosynthesis 7.4. Bibliography 8. Cell reproduction 8.1. The cell cycle 8.1.1. Interphase 8.1.2. Cellular division 8.2. Cellular division 8.2.1. Mitosis 8.2.1.1. Prophase 8.2.1.2. Metaphase 8.2.1.3. Anaphase 8.2.1.4. Telophase 8.2.1.5. Cytokinesis 8.2.1.6. More on mitosis 8.2.2. Meiosis 8.2.2.1. Meiosis I 8.2.2.2. Meiosis II 8.2.3. Meiosis and sexual reproduction 8.2.4. Meiosis and life cycle 8.2.5. Biological importance of meiosis 8.3. Differences and similarities between mitosis and meiosis 8.4. Bibliography 9. Classical genetics 9.1. Genetics basics 9.2. Mendelian genetics 9.2.1. The method 9.2.2. Mendel's Laws 9.2.2.1. Mendel's first law or principle of uniformity in the first generation 9.2.2.2. Mendel's second law or principle of segregation 9.2.2.2.1. Backcross and test crossover 9.2.2.3. Mendel's third law or principle of independent combination 9.3. Gene interaction 9.3.1. Gene interaction between allelic genes 9.3.2. Gene interaction between non-allelic genes that influence for the same trait 9.4. Chromosomal theory of heredity 9.5. Ligation and recombination 9.6. Complex mendelism 9.6.1. Multiple allelism 9.6.1.1. Lethal genes 9.6.2. Pleiotropy 9.6.3. Expressiveness and genetic penetrance 9.7. Sex-linked inheritance 9.7.1. Y-linked inheritance 9.7.2. X-linked inheritance 9.8. Heredity influenced by sex 9.9. Bibliography 10. Molecular genetics 10.1. DNA as hereditary material 10.2. DNA replication 10.2.1. The need for DNA replication 10.2.2. First hypotheses about DNA duplication 10.2.3. Meselson and Stahl experiment 10.2.4. The sense of growth of the new strands 10.2.5. Mechanism of DNA replication 10.2.5.1. Replication in prokaryotes 10.2.5.2. Replication in eukaryotes 10.2.6. Error correction 10.2.7. Enzymes involved in replication 10.3. Gene concept 10.4. "One gene-one enzyme" theory 10.5. Transcription 10.5.1. Mechanism of transcription 10.5.1.1. Transcription in prokaryotes 10.5.1.2. Eukaryotic transcription 10.6. Translation or protein biosynthesis 10.6.1. The genetic code 10.6.2. Mechanism of translation of RNA to proteins 10.6.2.1. Translation in eukaryotes 10.7. Regulation of gene expression 10.8. Bibliography 11. Genetics and evolution 11.1. Mutations 11.2. Types of mutations 11.2.1. Gene or point mutation 11.2.2. Chromosomal or structural mutation 11.2.3. Mutation at the genomic level 11.3. Causes of mutations 11.4. Evolutionary implications of mutations 11.5. Metabolic implications of mutations 11.6. Bibliography 12. Microbiology and biotechnology 12.1. Microbiology 12.2. Viruses 12.2.1. Viral morphology 12.2.2. Viral physiology 12.2.2.1. Lytic cycle 12.2.2.2. Lysogenic cycle 12.2.2.3. Cycles of viruses of special interest 12.2.2.3.1. Flu virus life cycle 12.2.2.3.2. Life cycle of the AIDS virus 12.3. Other acellular forms 12.3.1. Viroids 12.3.2. Prions 12.4. Biotechnology 12.5. Bibliography 13. Immunology 13.1. Infection concept 13.2. Defense mechanisms against infections 13.2.1. Nonspecific mechanisms 13.2.1.1. Primary barriers: external defenses 13.2.1.2. Secondary barriers: internal defenses 13.2.2. Specific mechanisms 13.3. Immunity and immune system 13.3.1. Components of the immune system 13.3.2. Concept and nature of antigens 13.4. The immune response 13.4.1. Humoral immune response: the antibodies 13.4.1.1. Antibody-producing cells: B lymphocytes 13.4.1.2. Antibodies 13.4.1.2.1. Types of antibodies 13.4.1.2.2. Antigen-antibody reaction 13.4.1.3. Immune memory: primary and secondary responses 13.4.2. Cellular immune response: T lymphocytes 13.5. Types of immunity 13.5.1. Natural immunity 13.5.2. Artificial immunity 13.6. Immune system disorders 13.6.1. Autoimmunity 13.6.2. Hypersensitivity 13.6.3. Immunodeficiency 13.6.4. Transplants and the phenomenon of rejections 13.7. Bibliography « Previous \| Next » 13.6.2. Hypersensitivity Hypersensitivity. Allergies The function of the immune system is to destroy foreign antigens without causing any harm to the person, but, on occasions, these responses can be of excessive force in the face of harmless or not very dangerous molecules, and can produce serious effects on people, even death. Two types of hypersensitivity are distinguished: Immediate or anaphylactic hypersensitivity: allergy The allergy is a hypersensitivity mechanism or exaggerated immune response to the presence of antigens safe or very dangerous. The immediate or anaphylactic hypersensitivity develops rapidly, about 10 to 20 minutes after exposure to the antigen, which in this case is called allergen. An allergen is a substance that induces a hypersensitivity (allergic) reaction in susceptible people who have previously been in contact with them. Some of the most common allergens are bee venom, pollen proteins, animal hair, dust mite feces, some medications like penicillin, some foods like shellfish, peanuts, etc. Development of the allergic reaction The allergic reaction develops following these phases: 1.- Allergen uptake by antigen presenting cells. 2.- Sensitization to the allergen. When the first contact with the allergen occurs, no external symptoms are shown, but the immune system recognizes the allergen since the antigen-presenting cells (APCs) phagocytize it and show its fragments in the MHC-II to the helper T lymphocytes (T_H), which recognize and activate neighboring B lymphocytes. The B lymphocytes into plasma cells and release large amounts of IgE immunoglobulins which bind to the constant region of basophils blood and mast cells tissues. This is the process of awareness raising. 3.- Release of the content of the histamine-filled mast cell granules. When the second contact with the allergen occurs, the allergic reaction occurs. The allergen binds to the IgE that coat mast cells and basophils, causing their degranulation, expelling substances from the cell cytoplasm. These secreted substances cause inflammation (histamines, prostaglandins, serotonin, etc.) and allergy discomfort, such as dermatitis or diarrhea, if it is a food allergy, mucus secretion if it is an allergy caused by substances contained in the air, etc. If mast cells and basophils discharge histamineblood, dilation will causes blood vessels, leading to a generalized reaction, with the contraction of the bronchioles and generally vasodilation can cause death by asphyxiation or a significant decrease in the blood pressure (anaphylactic shock). Delayed hypersensitivity It can also happen that the reaction occurs later, even several weeks after contact with the antigen, as in delayed hypersensitivity. Antibodies are not involved in delayed hypersensitivity, but rather a type of T lymphocytes that, after a second contact with the same antigen, release substances that stimulate the action of macrophages and trigger an inflammatory process. An example of this type of hypersensitivity is the cause of contact dermatitis caused by some cosmetics, clothing, jewelry or plants in contact with the skin, whose proteins bind with haptens present in these products and originate the antigens that trigger the disease. reaction. Since the symptoms (itching, rash, ...) are similar to those of anaphylactic hypersensitivity, these reactions are incorrectly called contact allergies. Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU) Aragon, September 2019, option B, question 5. Answer the following questions: (1 point) a) Define: autoimmune disease and allergic (or hypersensitivity) reaction. (0.5 points) b) Define passive natural immunity and give an example. (0.5 points) Aragon, June 2018, option B, question 1. Genetics and environmental factors play an important role in the origin of allergies. (1 point) a) What do we call an allergy? (0.5 points) b) What does the allergic response produce? (0.25 points) c) What is the nature of antigens and antibodies? (0.25 points) Aragon. June 2017, option A, question 5. Define the following concepts related to the immune system: hypersensitivity. (0.2 points) Aragon. September 2015, option B, question 5. Define the following statements: (2 points) Hypersensitivity reaction. (0.5 points) Aragon. September 2014, option B, question 4 . Define the following terms referring to immunity: (2 points) Allergic or hypersensitivity reaction. (0.5 points) Andalusia, September 2014, option A, question 5. Pollen is a foreign body for the body that, in allergy sufferers, causes annoying reactions (cough, sneeze, itching, nasal congestion). Why a first contact with pollen in these people may not cause external symptoms, which do appear after a second exposure? [0.5]. Does this mean that those allergic to pollen are immunodeficient? [0.5]. Reason for the answers. Basque Country, July 2020, option 3A It is estimated that in developed countries a high percentage of the population suffers from some type of allergy. a) (1 point) Indicate what an allergen is. Give some examples of allergens. Give reasons for your answer. b) (1 point) What type of immune system reaction occurs in an allergy? In this situation, what three basic processes can be triggered? c) (0.5 points) Mention one type of cell and one type of molecule involved in allergic processes. Madrid, July 2021, question A5 In relation to the immune response: Peanuts are one of the most common causes of food allergies. The hypersensitivity reaction appears within a few minutes of ingestion of this dried fruit. a) What is a hypersensitivity reaction? What is the difference between antigen and allergen? (1 point). b) Describe the processes that occur during an immediate hypersensitivity reaction using the following terms in the proper order: mast cell, allergen, histamine, IgE (1 point). Galicia, July 2021, question 8d Briefly: what are hypersensitivity and autoimmunity? Licensed under the Creative Commons Attribution Share Alike License 4.0 « Previous \| Next » These pages are semi-automatically translated from the web Biology 2nd Baccalaureate. Biología de 2º de Bachillerato (biologia-geologia.com). You can make any suggestion, question, comment, ..., in our forum 2º Bachillerato Biología - Foro de biologia-geologia.com
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