hello everyone information box ticket Lifestyles brings you today Immunology topic on antigen but before starting this video don't forget to like this video subscribe to my channel and press the Bell icon button let's see the table of contents first we'll go through the Indigent definition then properties of antigens anterior structure types of antigens antigen antibody complex antigenic samples and lastly applications of antigens let's learn about the antigen definition antigens are molecules or molecular structures that the body does not recognize and which often cause the formation of antibodies as a result of immunological response in simple words antigens can be anything that doesn't belong to the body and are foreign although the generation of an immune response is typically used to characterize antigens this is not always the case immunogens are the antigens that cause a reaction antigenic determinants of certain areas on antigen known to induce an immune response are necessary for antigens to do so to trigger a reaction the determinants attached to receptor molecules on immune cells that have a complementary structure the name AG denotes antigens which can exist as bacteria viruses chemicals pollen or other substances the ability of our body to discriminate between internal parts of the body and external particles give rise to the idea of an antigen the body produces antibodies that work against these antigens in response to these antigens proteins peptides and polysaccharides make up the majority of human antigens however lipids and nucleic acid can also function as antigens when mixed with proteins or polysaccharides in order to activate the body's adaptive immune system against antigen antigens may also be proposed fully injected into the body in the form of vaccinations now let's head to the properties of antigens antigens have a variety of characteristics that affect their immunogenicity making them crucial for comprehending the immune response to them these qualities are regarded as necessary to create a good antigen since they determine immunogenicity the following a few characteristics of antigens number one foreign nature all antigens that cause the horse to mount an immune response are external to its recipient's body the antigen is recognized by the host body as being distinct from the regular bodily parts with increase in the level of foreigners the antigen's immunogenicity Rises in the case of biological agents the foreignness increases with the increase in the phylogenetic gap between the two species there are certain exceptions though in that some proteins produced by the host may also trigger an immune response as in the case with auto antigens similar to this if proteins of other molecules from other species lack antigenic determinants or epitotes they can similarly fall to elephant and immune response number two chemical nature proteins and polysaccharides are the most powerful and often encountered antigens yet when they combine with proteins in polysaccharides other compounds including lipids and nucleic acids can also function as antigens for proteins the immunogenic portion of an antigen must have at least 30 percent of amino acids such as lysine glutamine Arginine glutamic acids asperging and aspartic acid as well as significant amount of hydrophilic or charged groups with the hydrogenicity of the molecules the amount of immunogenicity likewise Rises generally speaking homopolymers are less immunogenic than heteropolymers number three molecular size the immunogenicity of the molecules is also greatly influenced by the antigenous molecular size antigens must have at least 50 000 deltone in size in order to qualify as immunogenic according to accepted standards yet when combined with big Transporters compounds with low molecular weight must exhibit immunogenicity haptense or compound with lower molecular weight and at least one antigenic determinant are regarded as partial antigens number four molecular rigidity and complexity molecules rigidity and complexity are crucial aspects that affect their immunogenicity in comparison to less rigid molecules those that are stiff May produce antibodies to specific structures making them ideal antigens in journal the complexity of the structure is also important since peptide antigens with repeating units of only one amino acid are less immunogenic than those with repeating units of two or more amino acids number five antigenic determinants and cross reactivity antigenic determinants are parts of an antigen molecule that have a role in how antibodies respond with them antigens having two or more antigenic determinants typically can stimulate the formation of antibodies because a tiny molecule cannot have more than one antigenic determinant a smaller antigen often does not cause the formation of antibodies the ability of antibodies produced in response to one antigen to interact with another antigen is known as cross reactivity of antigens don't forget to subscribe to this channel now let's learn about the antigen structure the capacity of an antigen to attach to the antigen binding site of an antibody defines its molecular structure antibodies distinguish between various antigens based on a distinctive molecular structure that each antigen has on its surface the majority of antigens are polysaccharides or proteins they can be the Caps flagella poison fembrial and quotes of many bacteria viruses and microorganisms furthermore secretions and other substances of similar origin can function as antigens these microbes lipids and nucleic acids are only immunogenic when coupled with proteins and polysaccharides depending on the kind size and immunogenicity of the antigen it may also have a distinct shape every immunogenic antigen processes an exclusive structural element known as an epitode or an antigenic determinant the amount of epitotes varies between antigens in effect how many antibodies May bind to a particular antigen different structural elements of interaction in antigen dictate the kind of antibodies that they bind to a peritope is the area of an antibody that interacts with an antigen it has been determined that because the structure of an epitode and a peritope are distinct and complement one another they may also both be described as locks and keys now let's learn the types of antigens depending on a variety of variables antigens can be divided into many categories based on the antigens immunogenicity and place of origin certain categories are frequently used number one types of antigen based on their origin antigens can be classified into two groups on the basis of their Origins first is exogenous antigens exogenous antigens are those that come from outside the host body and are thus unfamiliar to the host these antigens may be ingested injected or inhaled into the body they then travel throughout the body with the help of bodily of fluids antigen processing cells such as macrophages and dendric cells play a major role in phagocytosis that is primary mechanism for the absorption of foreign antigens many antigens including intracellular viruses may start off as a foreign antigen before evolving into endogenous antigens extra will talk about endogenous antigens endogenous antigens are those that develop naturally in the host body as a result of intracellular bacterial or viral infection or during metabolism indogenous antigens are typically found in the body's cell or in the fragments substances or metabolic byproducts that are antigenic normally they are handled by macrophages before being found by cytotoxic T cells in the immune system xenogenic or heterologist autologous and idotype or allogenic antigens are examples of endogenous antigens due to the horse immune system's recognition of its own cell and particles as an immunogenic endogenous antigens may cause autoimmune disorders Auto antigens Auto antigens are host protein or protein complexes that the immune system of the host attacks leading to a autoimmune illness while the immune system shouldn't attack the body's own cells Auto antigens may be fatal to the host genetic and environmental factors cause the loss of immune tolerance to such antigens tumor antigens Neo antigenous major histocompatibility complex 1 and 2 present tumor antigens or Neo antigens on the surface of tumor cells the tumor-specific mutation that occurs during the manipulent transmission of normal cells result in the production of an antigens due to the retiver cell's ability to escape antigen presentation and immune defense these antigens often do not accent an immunological response native antigens native antigens are antigens that have not been altered by any antigen presenting cells making them inaccessible to immune cells like T cells yet even without any processing such antigens can activate B cells number two types of antigens on the basis of immune response based on the immunological responses there are two main categories of antigens first one is complete antigens immunogens complete antigens also known as immunogens are antigens that can cause particular immune reaction these antigens do not require any carrier particles to alicent an immune response they are often High molecular weight proteins peptides or polysaccharides greater than 10 000 deltons second incomplete antigens which is happens antigens that are incomplete are also known as heparins are unable to allocate an immune response on their own typically a carrier molecule is needed for these non-protein compounds to fully develop into an antigen few antigenic determined sites and a low molecular weight often less than 10 000 deltons characterize heptins the carrier molecules which is either a protein or a polysaccharide molecule is attached to the haptin and is regarded as a non-antigenic component kindly show your support to this channel by subscribing next is antigen processing and presentation antigen presenting cells break down antigens into smaller peptide fragments which are subsequently presented on the surface of the cell we are antigen presenting molecules like MHC class 1 and 2 to be recognized by lymphocytes antigen processing and presentation can occur with the help of three different pathways first one is endogenous pathway or classical MHC class 1 presentation the endogenous pathway of an antigen processing and presentation utilizes mechanisms similar to those involved in the normal turnover of intracellular proteins the proteosomes are specialized cytopolic proteolytic mechanism is used by the antigen presenting cells to break down the protein antigen into short peptides the immunoproteos nerms which is involved in the immune system contains components that are activated for exposure to interferons or t n f the amino peptidase in the endoplasmic reticulum Newman trims peptides as a next step in the proteolytic processes the transporter associated with antigen processing carries the peptides produced by proteolysis to the endoplasmic reticulum human the loading and trimming of the peptides on MHC class 1 molecule is mediated by tap tapsin and the calcinic calc reticulum system in addition to tab MHC class 1 molecules will either be delivered to the cell membrane or recycled by a process Valiant on UDP glucose glycoprotein transferase 1 depending on the Affinity of the loaded peptides in the case of high Affinity MSC class 1 complexes the peptides are delivered to the cell membrane with the help of Corgi apparatus in order to stimulate cd8 plus T cells responses that are specific for antigen number two exogenous pathway classical MHC Class 2 presentation in the exogenous rule the antigen is internalized by antigen presenting cells by straightforward phagocytosis once the substance interacts to certain surface receptors the endocytic processing Pathways uses the compartments of the cell to break down proteins into peptides the internalized antigen passes through several acidic compartments where it comes into contact with hydrolytic enzymes and low PH the MHC Class 2 containing compartments which is specific to the antigen presenting cells is where the ultimate protein breakdown and peptide loading occurs as antigen presenting cells Express both classes of MHC a unique mechanism exists to stop antigenic peptides from interacting with class 1 molecules the plus two chains connect with a protein known as invariant chain during the synthesis of Class 2 MHC molecules this protein blocks endogenously produce peptides from attaching to the class 2 molecules by interacting with the group that Vines Class 2 peptides the invariant chain deteriorates as it passes through several compartments eventually forming a brief piece known as clip Class 2 Associated invariant chain peptide afterwards an exchange of clip with an antigenic peptide is characterized by a Class 2 MHC protein the class 2 MHC molecule stability and structural Integrity depend on the peptide binding the class 2 MHC peptide complex is transported to the plasma membrane once the peptide has been bound with the neutral pH induces the complex to form a compact stable form number three cross presentation antigen presenting cells will use the exogenous Pathways endocytosis to redirect antigen to a Class 1 MHC loading and peptide presentation a process known as cross presentation yet in order for the phenomena of cross presentation to occur the internalized antigens must somehow be diverted to class 1 loading route from the external system handing Class 2 MHC presentation in the case of dendrix cells cross presentation is predominantly seen when it is accomplished by one of the two potential methods according to the first method cross-presenting cells have unique antigen processing equipment that permits peptides from external sources to be loaded onto a Class 1 MHC molecules according to the second process cells have specialized endocytosis equipment that sends in digested and Degen straight to the ordinary where the peptides are subsequently loaded onto class 1 MHC molecules the ability of antigen presenting cells to catch viruses for extracellular settings process them and activate cytotoxic T Cell lymphocytes that may Target virus infected cells which inhibit the propagation of the virus makes cross presentation of an antigen adventurous I would love to have you subscribe to this Channel Next is antigen antibody complex several antigens are born to antibodies to create a molecule known as antigen antibody complex or immunogenic complex the epitode and peritope components of the antigen and antibody respectfully Governor how well they attach to one another since antibodies can discriminate between many antigens they can fight against a variety of diseases the amino acid sequence of a species-specific epitote and peritope determines extremely particular nature of the interaction between antigens and antibodies an antigen antibody interaction produces the complex which is subsequently prone to a variety of reactions such as complement deposition obsonation and phagocytosis the proportion of antigrant to antibody determines the size and form of the immunological complex the impact of an immunological complex is in turn determined by size antigen antibody complexes have developed into a crucial tool for comprehending that interaction between antigens and antibodies and figuring out the mechanism behind molecular recognition between antibodies and antigens as the attachment of antigen to cell receptor initiate a signaling Cascade that activates antibodies immune complexes also play a part in controlling the generation of antibodies immune complexity are necessary for a variety of immunological tasks but their deposition can cause a number of autoimmune disorders including cyclotrima and arthritis next is antigen examples number one blood group antigens blood group antigens are proteins or sugars that are found on various parts of the membrane of the red blood cells the sugar generated by a variety of processes that categorize the transfer of sugar unit is what makes up the antigens in the blood type the type of enzyme involved which is in turn defined by the person's DNA determines the type of sugar in the red blood cell the DNA of the host also determines the proteins that make up the antigens for the RH blood type the D antigen which is present on the red blood cells as large protein is encoded by the rhd gene antigen antibody responses that help differentiate between various blood groups in humans they discriminate between these antigens number two bacterial capsule a polysaccharide layer that is present outside of the cell membrane and causes an immune response in the host is known as bacterial capsule being a well-organized coating that is difficult to remove the capsule is thought to be a potential factor in bacterial pathogenicity due to the need for capsule specific antibody to initiate phagocytosis the capsule may also play a role in some bacteria's ability to avoid it the polysaccharides component of bacterial capsule is conjugated with protein carriers and utilized as an antigen in vaccinations the exact structure function and involvement of capsule in bacteria differ in different bacterial species lastly application of antigens as antigens are often quite specific it is possible to distinguish between various bacterial species by looking for specific antigens in distinct species antibodies may be found in a sample using antigens which can also be employed as diagnostic tools antigen and antibody complexes which are used in forensic application to identify human blood and other materials depend on antigens as a key component for the measurement of diverse chemical and biological compounds they are also utilizing immunoassays autoimmune illnesses some of which are fatal are brought on by Auto antigens as a kind of passive immunity inactivated enzymes are employed in vaccines to treat and prevent many illnesses and that's it for today thank you so much for watching till the end don't forget to like this video subscribe to my channel and press the Bell icon button thank you so much for watching