Loading
Notes d'étude
Study Reminders
Support
Text Version

Basics of Immunology

Set your study reminders

We will email you at these times to remind you to study.
  • Monday

    -

    7am

    +

    Tuesday

    -

    7am

    +

    Wednesday

    -

    7am

    +

    Thursday

    -

    7am

    +

    Friday

    -

    7am

    +

    Saturday

    -

    7am

    +

    Sunday

    -

    7am

    +

Video 1: Types of Immunity
Good morning everyone. Hi I am Hemalatha Kanniyappan doing my research under the guidance of DoctorVignesh Muthuvijayan . Today I will be giving a lecture on immunology, the main lectureis based on immune responses to foreign material or biomaterial or any implant .So, before weunderstand orgo deep into the understanding of immune responsesin the presenceof biomaterial , we should note few basics of immunologicalresponses or immunologicalterms and or what is immunology or what are the cells involved in immune responses andall . So,in this lecture I will begiving a briefintroduction about what is immunology orwhat are theimmunity immune responses or what arethe types of immune responses or what are the cells or organs involved in immune systemand the major cells which are responsible for a immune responses . So,we should knowwhat is immunology . So, what is immunology? It is just the study of a biology which studiesthe immune systems of for organisms or a what do you mean by immunity , we say right youhave a very good immunea immune response of this kind of infection or ah. So, what doyou mean by that ? So, what is immunityimmunity? Is nothing, but the protection of body againstpathogens or infectiousinfections caused by pathogens . When I say pathogens; pathogensare like viruses, bacteria, fungi, parasites or some proteins .So, this is about immunity and what is pathogen and there are two types of immunity ; innateimmunity and adaptive immunity.

Video 2: Cells of the Immune System
When I say it is innate immunity it is the primary formof defense mechanism in our body. So, our body it itself as a defense mechanism likeit is a very good ah; it is very good defense force to act against the pathogens which entersthe body . So, it is divided into innate and adaptive immunity .So, innate immunity where innate immunity is like it is always on ok,it isit is presentfrom the birth this is the primary form of defense mechanism . So, always on which meansit has barriers when I said barriers it means what? What are the barriers that protect ourbody from the pathogens ? The first and foremost is skin . Skin is the largest organ of thebody it protects our entire body from various pathogens entering into our body .The next one is mucous membrane mucous. There are several places in our several parts ofbody are covered by . Mucous which protects the those partsfrom the pathogens mucous arenothing, but the two or more layers of epithelial cells . And then p H , the acidic p H of ourstomach which is like around two to threea very acidic which kills the bacteria effectivelyskin mucous membrane pH. Then microbial flora which is present in our body there are somegood bacteria's in our gut which protects our body from the pathogens.So, these are the main barriers present from our birth forto fight against the pathogens.Then again in innate immunity this part of thecells are always present ok always on nomatter what the pathogen enters it we will go on a kill that it will go on act againstthat pathogen. The next is immunity immediate response where the cells present in thislikethey are not activated all the time, but once when the pathogen enters it immediately actactive gets activated and start acting or fight against the entering pathogen for example,blood cells . So, these blood cells it will be there intheit will go it will be there in the bloodstream, but once when the pathogen enters it willgo get activated and fight against those pathogens . And one more thing in always on kind ofa immunity there is one compliment factors . Compliment factors are not the cells theyare kind of proteins proteins which acts against the pathogen not cells ok which acts againstthe pathogen. So, this is about the innate immunity andthe next one is acquired immunity or adaptive immunity. It is more specific and specializedkind of a response which becomes part of our immune system at a later stage which meansit is not an immediate response it is a kind of delayed response ok .So, adaptive immunity is delayed response . So, the major cells responsible for thistype of immunity is lymphocytes . Lymphocytes again divided into T cells and B cells andnatural killer cells ; T cells, B cells and natural killer cells ok. And this B cellsproduces antibodies ; these B cells produces antibodies which fight against the pathogenand T cells again T helper cells and T cytotoxic cells are there ok.Natural killer cell different differed distinguish from T cells and B cells with the presenceof where B cells and T cells at the specialized receptors on the surface natural killer cellswill not have that that is a major difference between these cells ok. So, when I say theimmunities based on the cellsbecause of the cells where in innate immunity or as wellas in theadaptive immunity when I say the immune responses because of the cell it iscalled cell mediated immune response ; cell mediated immune response .The other immune response is mainly based on proteins or these antibodies they are notcells which are termed as humoral mediated immune response .These are the two major immune responses which act in our body. So, in this slide where innateimmunity is nonspecific resistance which means no matter what the pathogen is.Once it enters the bloodstream it will go on and engulf and it will kill the pathogenthat is nonspecificimmunity whereas, the adaptive it is more specific it will go and kill themost specific antigen or a specific it will produce a specific antigen to killed thatthe specific pathogen ok specific resistance responses to the immune system .So, the first line of defense we all know that the barriers that the barriers are nothing,but skin, mucous membrane were or for example, for mucous membrane its like a nose,eyes,lipsand all where eyes is covered by mucous membrane it is not covered by skin . Which protectsour eyes from the external pathogens and normal microbiota present in our gut. Our gut willproduce a good bacteria to engulf the bad bacterias also the p H .And the second line of defense are the phagocytes; phagocytes which engulf the micro organismsmainly of WBC cells . And the third line of defense which are the adaptive immunity specializedlymphocytes. The lymphocytes are the major cells responsible for this central cells forthe adaptive immunity which again divided in to B cells and T cells and the B cellsproduces antibodies; antibodies whichfight against the pathogen.So,these are the specific nonspecific host defenses summary of nonspecific innate immunityanatomic barriers which are skin , mucous membrane. The skin is the largest organ ofthe body and it plays a very important role in our defense mechanism and mechanical barrierwhich stops the entry of microbes on the first step itself .And acidic enrollmentstomach acidicwhich digest the bacterias and mucous membrane; mucousmembraneagain helps the helps to protect the entry of microbes into the internal organs. And the physiological barriers like temperature, low p H that which I said already acidityof stomach and chemical mediators or the factors complement factors .And phagocytic or endosytic barriers where all the various type of cell which will endocytose;endocytoses nothing, but the engulfingcells and breaking down into foreign molecules andthe cells responsible for those are macrophages neutrophils monocyte and tissue macrophages. And inflammatory barrier where the tissue damage on infection induce leakage of vascularfluid this contains the serum proteins which as the antibacterial activity and in in tothe affected area . So,this is the principle mechanism of innateand adaptive immunity in terms of adaptive immunity the adaptive immunesystem as forimportant characteristic attributes. The first one is antigen specificity , these are thecharacteristics of adaptive immunity . The second one is diversity ; diversity , thirdone is immunologic memory and the last one is self non self recognition; non self recognition . First attribute characteristic attribute isantigen specificity . So, it permits the immune system to distinguish even a small differenceamong the antigens. So, it will be more specific in in recognizing the antigen and diversityit allows the immuneadaptive immune system for generating tremendous ina diversity ofrecognition molecules; recognition molecules in allowing that torecognize billions of uniquestructures present in the foreign antigens that is diversity.And immunologyimmunologic memory once the immune system recognize the antigen and respondedto the antigen . When the same antigen it encounters the second time for the secondtime it will develop the high level of immuneresponse immuneto that specific pathogen it . It keepsthat in his memory that we have encountered this already and we became immune to that. So,this is thethis attribute is a very important attributein adaptive immunity.And the finally, once it is responded and the immune systemshould be able to differentiatefrom the self and the nonsensecomponents in order to act on the non self components ifthe. So, what will happen when the immune system fails to recognize between or differentiatedbetween the self and non selfcomponents? Yes; obviously, it will lead to some other responsesand it it could be fatal . So, these are the major four importantcharacteristics of a adaptivehumanity. So, the principle mechanisms of adaptive immunity. So, main is microbes, epithelial barriers, phagocytes compliment and in where in caseof adaptive immunity B lymphocytes and T lymphocytes; B lymphocytes producers antibiotics antibodiesand T lymphocytes. So, they affect our T cells t h cells and t c cells.So,this is all about the types of immunity liketo summarize that innate immunity andadaptive immunity innate; immunity is nonspecificresistance like whatever the pathogen it enters entersthe body it will go onoh act on the fight against that pathogen. Whereas, the adaptiveimmunity its not anspecificits it s like completely specific to thepathogen and fight againstthat pathogen and it is also termed as delayed response . Adaptive immunity is also a delayedresponse termed as delayed response immune system immunity.Whereasinnate immunity it act as immediately there is immediate response as well as alwayson responses that is be some barriers which are always on in the innate immunity . Andmajorcells present in innate immunity is like a skin or the epithelial cells and microbesand there alland few are chemical factors or physical factors are also involved liketemperature or p H and chemicals cytokines. Andthey those are involved in innate immunityadaptive immunity major cells in adaptive immunity or lymphocytes ok . So, this is allthis all aboutimmunity. Now, we will go to the cells present in theimmune system; cells of the immune system .

Video 3: Macrophages and Phagocytosis
So, and this picture is theprocess of hematopoiesis; hematopoiesis has nothing, but the formation of blood cells . So, any blood cells willoriginate from the hematopoietic stem cell .Blood stem cell is nothing, but hematopoietic stem cell we just self renewing cells ok.And this self renewing cells we will give rise to either of myeloid progenitor cellsor lymphoid progenitor cells these are progenitor cells. When I say they are progenitor cellsit willwhich means it losses the self renewing capacity and it will be specific to a particularcell lineage ok. And myeloid stem cell progenitorsprogenitorcells lymphoidsprogenitor cells and this hematopoietic blood cell originated from bone marrow . So,that is the place where this hematopoiesis takes place. 2 major cell linages is lymphoidcell linage and myeloid stem cell linage . So, myeloid stem cellprogenitor cell willgive rise to granulocyteprogenitor cells, basophil progenitor cells, eosinophil progenitorcells from the granulocyte it will give rise to neutrophils , monocytes. And this monocytesgive rise to macrophages ok which are very important cells responsible forimmune systemimmunity andneutrophils monocytes, macrophages. And neutrophilprogenitor cells give raisedto neutrophils and basophil progenitor cell eosinophil, progenitor cells give rise toeosinophils ok . Also erythrocyte progenitor cells which give rise to red blood cells andmegakaryocytes; megakaryocytes which gives riseto platelets ok. So, this is the this all about the myeloidlineage it also give rise to dendritic cells ok. Dendritic cells are antigen presentingcells they are APCs, Antigen Presenting Cells ok . Andthis all about myeloid stem cell linagewhich is nothing, but which gives rise togranulocyteprogenitor cell basophil, eosinophil and granulocytesagain give raise to neutrophils as well as monocytes from monocytes macrophages are originated. And it also give rise to megakaryocytes withfrom which platelets cells or platelets originates and thenerythrocytes from which RBCs, theseall about myeloid lineage. Where as in lymphoidstem cell lineage when it gives rise to lymphocytelymphocyte which are again divided into B lymphocyte, T lymphocyte and natural killercells ok also it gives rise to dendritic cells. So, these are theagain these are we all knowthese all the WBC cells White Blood Cells. So, in this natural killer cells mainly differfrom B lymphocyte on the T lymphocytes with the presence of surfacethe presence or absenceof surface receptors. Where in B cell and T cell have the present have the surface receptorswhere as in natural killer will do not have and it iscalled as the large cell it is alarge cell and where as b and T are a small nave cells ok.These are about the cells of the immune system and we should we should know about the beforegoingin depth with the cellsI will tell about the organs of the immune system ok. There areitis divided into primary organ ; primary and secondary ok. In primary bone marrow and thymusthese are the organs responsible for the production of T cells and secondary lymph node and spleenok. So, this primary organs where itit it is thesite for the maturation of the cells B cells or the T cells ok , this is the maturationsite . Once it got matured it acts against the pathogen right it will go and fight againstthe pathogen that will act in the secondary organs which are action site .This is a basic a few a few points you should know when you know when you study about immunesystem . The organs of the immune system which are the primary lymphoid organs or the secondaryorgans . In primarywhich is the place for the maturation of the cells bone marrow andthymus for B cells and T cells . And the secondaryorgans are lymph node and spleen where it it willbe an action site for the matured cells to act against the pathogen . So, this all aboutthe organs and the cells of the immune system ok.And the morphology and staining characteristics of the various type of blood cells. So, fromthis the large lymphocyteas I said as I said in the previous slide the large lymphocytesare nothing, but natural killer cells ok. and the small lymphocytes are nothing, butB cell and T cell ok. And these are the small cells have the redcells or the red blood cells and monocyte; monocytes are also present and the basophils,eosinophils are also present. So,both red blood cells platelet they lack nucleus andthey are the most numerous cells present ok. Most numerous of the leukocyte populationare neutrophils, the in the next slide you will be seeing the percentage of differentcell types in present in the WBC. And lymphocytes are the predominant cell type for responsiblefor the immune response ok they are the central cells for the responsible for the immune response. So, this slidewill tell you what the percentageof cells present in the wwhite blood cells. So, neutrophils or neutrophils it is likea it occupies like 60 to 70 percent ok and your basophils and eosinophils basophils 0.5to 1 percent, eosinophils 2 to 4 percent, monocytes 3 to 8 percent and lymphocytes 20to 25 percent. And in this neutrophils and eosinophils are again phagocytic cells; neutrophilsand eosinophils basophils are non phagocytic ok. Monocytes give rise to macrophages B cellsT cells ok. So, in thisthisclassification is mainly basedon the granulation and thestaining characteristic of cells. So, a granular and granular itsbased on the presence of granuous in the cytoplasm whereas, alsobased on the classification ofthe nuclear ok . Based on the classification of morphology , based on the difference inmorphology and staining characteristic or granulation or granulation .So, lymphocytes and monocytes a granular, it does not have granular in the cytoplasmwhere as basophil neutrophil and eosinophil as granules in the cytoplasm . And the neutrophilsor a as a multilobed nucleus multilobed nucleus ok and it will stain with both acidic andbasic dyes; stains both as acidic and basic dyes ok.And eosinophils; eosinophils is a it has a bilobed nucleus; bilobed nucleus where itstains only with the acidic dye eosin red that is why its name as eosinophils only acidicdye. It stains with only acidic dye eosin red and whereas, basophils stains only withbasic dye methylene blue ok. So, these all about the classification based on the morphologyand staining characteristics or granulation present in the cells .And this this picture summarizes the all the cells present in the immune system which areresponsible for the immune responses . So, cells of the immune system in for innate immunesystem, for adaptive immune system were certain cells which are produce in both in bothinnateand adaptive immune system . Whereas neutrophils,monocyte, eosinophils,basophilsor present innate immune system whereas, T cell B cell. So, when I say it is an innateimmune system it these cells will be there always ; always on and when a pathogen comesit will go on act again the pathogen no matter what the pathogen is or what the antigen is. But whereas, when I says the cell of adaptiveimmune system they are the delayed respond they act against the specific antigen whichare T cell B cell and T helper cell and T cytotoxic cells and both immune system hasmacrophagesand dendritic cells macrophages for the phagocytic activity .So,sowith thisslide we know about what are the immunity and what are the immune responsesand what are the cells present in the immune system and what are the organs of the immunesystem. So, next I will talk about macrophages . So,macrophages are nothing, buttheywe can say the enlarged monocytes ok. Monocyte circulatein a a bloodstream for a period of 8 hours during which they become enlarged and go toa specific tissue where they become the way fused together and enlarge and become an macrophageok ; macrophage. So, the main difference between monocyte andmacrophage is in this structure ok . The structure of macrophages 5 to 10 fold larger than themonocytes; larger than the monocytes also, the number of organelles and its complexityis increased then the monocyte especially lysosomes. It the number is increased a lotas well as its complexity also it produces hydrolytic enzymes .So, this is the major difference between macrophage and the neutrophils neutrophils will not producethe hydrolytic enzymes other than that it will go on and phagocytize in the similarway of the macrophage do, but the macrophage secret side of lyticenzymes and some solublefactors as well as . So, macrophages the fused enlarged form of monocyte ok ah.When it go migrates and go deposited to a specific tissue it becomes a tissue specificmicrophage and these are the same images of the macrophage. The first is the macrophagessame image where it does not know like very long pseudopodia and it acts against the bacteriaright. And this is the macrophage , pseudopodia , bacteria ; the same is here, but this oneas our erythrocytes. So, how beautiful it is the macrophages areright macrophages are very beautiful know because they are very important to our immunesystem to fight against the pathogen , we should prays them of course, .And specialized macrophages; specialized macrophages to go and deposited in the tissue and we wouldbecome the tissue specific macrophages and here we have given the few examples of tissuespecific macrophages . So, the macrophage in the lung or alveolarmacrophages and kupffer cells in the liver, osteoblast in the bone microglia in the centralnervous system which is in the brain . Histiocytes in connective tissue mesangial cells in akidney these are the tissue specific macrophages .And this is this or diagram a shows the maturation of macrophage first the stem cell and themono blastto that it farms and monocyte monocyte originate from thismono blast and that monocytefusedand forms an enlarged one macrophage. Once it activates it is an activated thereare two types like resting macrophages and activated macrophages. One resting macrophagesit will go and sit in one place , it will take rest. Once the one someone calls it likewhen it gets some signal or then it will act against the pathogen, but certain macrophagesare active throughout activated macrophages are more effective than the resting macrophagesthat; obviously, right when like a person who is very active is more effective thana person who sits in the same place for all the time .And these are the issues specific macrophages and the lowerpicturea lower panel shows theactivated macrophages, you can see how large it is. The activated macrophage in terms ofmorphology I also though presence oforganelles in number as well as its complexity that thecomplex structure . So, activated macrophages are veryeffective, then the resting macrophages.So, activated macrophages ; activated macrophages are more effective than the resting macrophagesinin killingpathogens for several reasons . They are like it has increased phagocyticactivity and it produces increased production of inflammatorymediators also it producesspecial cytotoxic proteins these proteins can actagainst severalpathogens like specific pathogens. Like cytotoxic proteins tag against into acertain broad range of a bacterias , it acts this cytotoxic protein like acts against theinfected. This cytotoxic protein acts against the broad range of targets including intracellularbacteria , broad range of targets including intracellular bacteria virus infected cellsincluding intracellular or cancer infected cells. Intracellular bacteria , virus infectedcells or cancer cells. So, these all about the activated macrophages yeah.So, normally in resting statenormally inresting state macrophages are activated by a varietyof stimuli in course of immune response . So, there are certain macrophages which will bein a resting state which starts to activate one to get the signal from the other cellsand phagocytosis is an important activating stimulus ok. Phagocytosis is the importantactivated phagocytosis is nothing, but the engulfing of the pathogen .So, again the macrophages are further activated by cytokines secreted by T helper cells . So,in this way in the in the entire immune responses or a immune system this macrophages and andT helper cells facilitate with each other ; macrophages and T H cells andthey are themediators by the . Also it activatesstimuli mediators by the response inflammatory responsethese are the certain stimulus for the resting macrophages to get activated .Next is the phagocytosis; phagocytosis are nothing, but the engulfing of the foreignmaterial ok. There are 3 steps; first it has to go and recognize what is the pathogen andthen the neutrophil gets attached and engulf there by once it engulf the lysosome and everythingall enzyme acts on it kill it and degrade it.So, engulf andyeah engulfment and degradation may not happen with the biomaterials yes rightthe bio materials will be large enough for that the phagocytes go on engulf it. So, itcannot do that for the biomaterials . It it is a differenttype of phagocytic cannot saya phagocytic it is in a foreign body reaction will happen when the in the presence of biomaterials; foreign body reaction will happen in the presence of implant or a biomaterials.So, these are the steps of phagocytosis for the engulfing and pathogen. The first bacteriumbecomes attached to a membrane called pseudopodia then once it isattach it is ingested forma phagosome and then phagosome fuses with lysosome . And this lysosomal enzyme digestthe captured material finally, the digestive products released from the cells. But if thistarget if a phagocytosis is cytosis fails to engulf the target it will become more frustration.See if I have given if I have given some work to do if I did not do that; obviously, mymy senior or the guide who gave me this work will become frustrated or even me even meas well I will become frustrated right . So, the same thing will happen to phagocytosis. Because it cannot do the work what it is given to is or given to him.So, that is whyit is termed as frustrated phagocytosis ok. So, now, I will be showinga small video about the process called phagocytosis. What are phagocytosis? The engulfing of thebacteria by the immune cells . So, what are the immune cells which play avery important role in phagocytosis? Macrophages . So,now look into the video you will understandeven more better. So, those are the cells are macrophages which engulfing the bacteriathey eat and destroy the bacteria. They are the white blood cells which are calledas macrophages. See how they are invading, its very beautiful right.So, the main job is to eliminate foreign entities that invade your body.Which is through the process called phagocytosis. See these bacteria known as soon as it enters,it release some proteins which go on alert the macrophages to start its function.These macrophages attaches to that bacterium with the help of special proteins that arepresent on the cell surface. Then the bacterium is engulf and locked insidea structure called phagosome, then it is cleaved and destroyed by the digestive enzymes intopieces. And these resulting particles can be eitherused by the cell or get out of the cell released out of the cell .And there it leads to the foreign body giant cells. The foreign body giant cells are thelarge cell which arewhich are formed as a result of fusion of macrophages ok that happensin the presence of bio materials as I explainedbefore. So, biomaterial cannot be engulfed by thephagocytosis. So, if any implant or any biomaterial are place inside there are series of reactionswill happened ok. In that reaction foreignbody giant cell playtakes place a very important role in that . So, a foreign body reaction, if I say foreignbody reaction it is mainly due to the presence of macrophages and the foreign body giantcells ok. So,again the blood tissue and tissue biomaterial interaction and the biomaterial.So, see monocyte tissues the blood and tissues and when they place a biomaterial there willbe some interaction between tissue and biomaterial right .So, they are macrophages will there and in the biomaterial foreign body giant cells willform. So, the we have huge mass surrounding the biomaterial which the presence of macrophagesand foreign body giant cells . So, foreign body giant cell is the collection of fusedmacrophages in the presence of because of the presence of foreign body ok large foreignbody . So, the adhesion of macrophages and foreignbody giant cells at the surfaces of biomaterial exists betweenproducers and environment thatexists between the cell membrane and surface of the biomaterial . So, I will ask you onequestion. So, if I want to place a bio material whatare the factors you need to consider for animmune response, for an what do say for an advantageousimmune response. There are see we cannot directly plays an biomaterial inside our body withouta proper understanding of the immune responses or the proper understanding of the propertiesof the biomaterial right. So, what are the properties you need to thinka lot for an invivo application or as a implant? Main thing is size and surface chemistry.Surface chemistry of a biomaterial any material biomaterial if placing a inside our body orplacing invivo its very important ok surface chemistry .So, there should be some compatibility right; compatibility between tissue and the biomaterialsee there are two in interaction majorly takes place cell cell interaction, cell tissue interactionoh sorry cell cell interaction and thetissue biomaterial interaction. Tissue bio materialinteraction should be proper that then only it become nontoxic otherwise compatibilitywill be of question mark; compatibility means the safety ok .


Video 4: Inflammatory Response
So, you need to consider the surface chemistrydegradation of degraded products like whether it the degradingproducts or leach ate from the bio material should not should be nontoxic and the sizesurface chemistry geometry everything you need to be considered for thefor degradingthe immune response . So, inflammatory response. So, inflammatoryresponse it is the localized nonspecific response to infection or wound it just the physiologicalresponse as a result; physiological response as a result of a infection or injury thatis the inflammatory response the immediate response in our body . Tissue damage whicharedue to the pathogen invading or invading pathogen or a wound which induces the complexsequence of events that stimulate the immune response right .That is collectively termed as inflammatory response . If my tissue is getting damagedthere will be a sequence of events takes place in order to repair this tissue . So, becauseour immune system is more effective by its own right to repair tissue . So, that collectivecollectivelyknown as inflammatory response, the inflammatory response is this complex sequence of eventsthat happens when the tissue is injured or damage ok .So, in this session we learnt about the what is immunity and what are the cells involvedin immunity and what are the organs of the immune system as well as the few basic stepsof inflammatory response. Thank you .