Components of the immune system

Molecules involved in the immune system

Antigens

An antigen is any substance capable of triggering the immune response and inducing the formation of antibodies.

An antigen can be any protein or polysaccharide that is foreign to the body.

The epitope or antigenic determinant is a small portion of the antigen that is recognized by the antibody, to which it binds.

Antibodies

The antibodies or immunoglobulins are glycoproteins produced by B lymphocytes having a three dimensional structure that allows them to bind antigen by the binding site, called paratope.

Antibodies can act as surface antibodies, if they remain attached to the membrane of the B lymphocyte, or circulate through the blood or other body fluids, such as breast milk, tears, etc.

Major histocompatibility complex

The Major Histocompatibility Complex (MHC) is made up of a set of genes whose products are expressed on the surface of cells of the immune system. The immune system recognizes the glycoproteins and glycolipids of the plasma membrane of these cells as its own and this means that the immune response is not triggered, with the exception of autoimmune diseases.

The MHC was discovered for its involvement in the acceptance or rejection of organ and tissue transplants, which is why it was given that name.

The molecules synthesized from the MHC intervene in the development of specific immune responses, both humoral and cellular, since they intervene in the recognition of the antigen by T lymphocytes (helper, T_H, and cytotoxic, T_C).

Two types of major histocompatibility complex (MHC) are distinguished:

MHC-I: determine membrane glycoproteins that appear in almost all cells of the body, and serve to present peptide antigens from altered self cells (cancerous or virus-infected) to cytotoxic T lymphocytes (T_C).
MHC-II: determine glycoproteins of antigen-presenting cell membranes (macrophages, dendritic cells, B lymphocytes), and serve to present exogenous peptide antigens (of the infectious agent) to T helper lymphocytes (T_H).

Lymphocytes

The lymphocytes are a type of leukocytes (white blood cells) are found in blood and lymph. Its nucleus is large and rounded, and it has little cytoplasm. They cannot form pseudopods and therefore do not engulf. Its main function is to regulate the specific (or adaptive) immune response, reacting against foreign materials (microorganisms, tumor cells or antigens in general).

There are the following types of lymphocytes:

B lymphocytes. They develop and mature in the bone marrow and then migrate to different lymphatic tissues. They are responsible for the humoral immune response, transforming into plasma cells or plasma cells that produce antibodies (specific proteins) in the presence of antigens.
T lymphocytes. They are formed in the bone marrow and develops in thymus and involved in cellular immune response. They do not produce antibodies, but instead cause the death of certain cells that are altered and, therefore, unwanted. There are three types of T lymphocytes:
- Helper T lymphocytes (T_H). They recognize antigen-presenting cells and activate B lymphocytes.
- Cytotoxic T lymphocytes (T_C). They recognize the antigens that are attached to the cells of the body, and destroy them, acting on cells infected by viruses or tumor cells.
- Suppressor T lymphocytes (T_S). They suppress the autoimmune response that can destroy cells in your own body, they act at the end of the immune response.

NK (natural killer) cells destroy infected cells. The T lymphocytes and B have specific receptors but not NK cells.

Lymphoid organs

The stem cells of lymphocytes, like those of other blood cells, are formed in the red bone marrow and are transformed into mature lymphocytes in the lymphoid organs. There are two types of lymphoid organs:

Primary lymphoid organs. In them the definitive maturation of the lymphocytes takes place and they are:
- The bone marrow. The B lymphocytes they mature in the red bone marrow.
- The scam. The T cells leave the bone marrow and mature in the thymus, gland located between the sternum and the trachea, and that increases in size until puberty, and then taper off.
Secondary lymphoid organs. Lymphocytes accumulate in these organs and there they undergo a final differentiation. Mature lymphocytes arrive and contact antigens to initiate the immune reaction.

The main secondary lymphoid organs are: the spleen, the lymph nodes (located along the lymphatic system, being more abundant in the groin, armpits, ...), the appendix, the intestinal peyer's patches, tonsils and adenoids.

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

Murcia, July 2021, question 4.7

List the two main types of lymphocytes, the organs where they mature, and the type of immunity in which each of them participates. (1 point)

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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 » 13.3.1. Components of the immune system Components of the immune system Molecules involved in the immune system Antigens An antigen is any substance capable of triggering the immune response and inducing the formation of antibodies. An antigen can be any protein or polysaccharide that is foreign to the body. The epitope or antigenic determinant is a small portion of the antigen that is recognized by the antibody, to which it binds. Antibodies The antibodies or immunoglobulins are glycoproteins produced by B lymphocytes having a three dimensional structure that allows them to bind antigen by the binding site, called paratope. Antibodies can act as surface antibodies, if they remain attached to the membrane of the B lymphocyte, or circulate through the blood or other body fluids, such as breast milk, tears, etc. Major histocompatibility complex The *Major Histocompatibility Complex* (MHC) is made up of a set of genes whose products are expressed on the surface of cells of the immune system. The immune system recognizes the glycoproteins and glycolipids of the plasma membrane of these cells as its own and this means that the immune response is not triggered, with the exception of autoimmune diseases. The MHC was discovered for its involvement in the acceptance or rejection of organ and tissue transplants, which is why it was given that name. The molecules synthesized from the MHC intervene in the development of specific immune responses, both humoral and cellular, since they intervene in the recognition of the antigen by T lymphocytes (helper, T_H, and cytotoxic, T_C). Two types of major histocompatibility complex (MHC) are distinguished: MHC-I: determine membrane glycoproteins that appear in almost all cells of the body, and serve to present peptide antigens from altered self cells (cancerous or virus-infected) to cytotoxic T lymphocytes (T_C). MHC-II: determine glycoproteins of antigen-presenting cell membranes (macrophages, dendritic cells, B lymphocytes), and serve to present exogenous peptide antigens (of the infectious agent) to T helper lymphocytes (T_H). Lymphocytes The lymphocytes are a type of leukocytes (white blood cells) are found in blood and lymph. Its nucleus is large and rounded, and it has little cytoplasm. They cannot form pseudopods and therefore do not engulf. Its main function is to regulate the specific (or adaptive) immune response, reacting against foreign materials (microorganisms, tumor cells or antigens in general). There are the following types of lymphocytes: B lymphocytes. They develop and mature in the bone marrow and then migrate to different lymphatic tissues. They are responsible for the humoral immune response, transforming into plasma cells or plasma cells that produce antibodies (specific proteins) in the presence of antigens. T lymphocytes. They are formed in the bone marrow and develops in thymus and involved in cellular immune response. They do not produce antibodies, but instead cause the death of certain cells that are altered and, therefore, unwanted. There are three types of T lymphocytes: Helper T lymphocytes (T_H). They recognize antigen-presenting cells and activate B lymphocytes. Cytotoxic T lymphocytes (T_C). They recognize the antigens that are attached to the cells of the body, and destroy them, acting on cells infected by viruses or tumor cells. Suppressor T lymphocytes (T_S). They suppress the autoimmune response that can destroy cells in your own body, they act at the end of the immune response. NK (natural killer) cells destroy infected cells. The T lymphocytes and B have specific receptors but not NK cells. Lymphoid organs The stem cells of lymphocytes, like those of other blood cells, are formed in the red bone marrow and are transformed into mature lymphocytes in the lymphoid organs. There are two types of lymphoid organs: Primary lymphoid organs. In them the definitive maturation of the lymphocytes takes place and they are: The bone marrow. The *B lymphocytes* they mature in the red bone marrow. The scam. The *T cells* leave the bone marrow and mature in the thymus, gland located between the sternum and the trachea, and that increases in size until puberty, and then taper off. Secondary lymphoid organs. Lymphocytes accumulate in these organs and there they undergo a final differentiation. Mature lymphocytes arrive and contact antigens to initiate the immune reaction. The main secondary lymphoid organs are: the spleen, the lymph nodes (located along the lymphatic system, being more abundant in the groin, armpits, ...), the appendix, the intestinal peyer's patches, tonsils and adenoids. Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU) Murcia, July 2021, question 4.7 List the two main types of lymphocytes, the organs where they mature, and the type of immunity in which each of them participates. (1 point) 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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