Cell Recognition & The Immune System

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of blood and into other tissues. vessels chemical products of the pathogen attract the phagocyte - it moves towards the pathogen along a concentration gradient (ATTRACTION) →lysosome nucleus lysosomes within phagocyte migrate howards →pathogen several receptors on Phagocyte has cell-surface membrane that attach to chemicals on the surface of the pathogen. CATTACHMENT) the phagosome, formed by engulfing bacteria. (ENGULEMENT) chemical e Sphagocyte, pathagen →phagosome Forming. (4) The lysosomes release their Tysozymes into the phagosome, where they hydrolyse the bacterium. CDIGESTION) breas of n parhagen phagosome Hlysosomes release lysozymes into phagasay hyanolysis product of the bactenum are absorbed by the phagocyte. (ABSORPTION + DISPOSAL) 6 Phagocyte will attach the antigen to the surface of the phagocyte in the complex MHC. >Recognition of self and non-self: Limmune immune system identifies matter that wn't part of us. (non-self) to be able to attack it. it also identifies this from self and not attack it. LAll cell types, viruses, hoxins and organic material has proteins or marker molecules the surface to identify them. Antigen = molecule that induces an immune response in the body can be proteins or glycoproteins. Specific immune system has the ability to target these different antigens and respond to them specifically. SIS lymphocytes) use that shape of the molecules to identify the non-self matter needing to be destroyed. Your system has millions of different lymphocytes capable of identifying all sorts of infections, these are produced very early in development, and remain in the body through life.. Why does our immune system not attack 'self '? protein markers (for example MHC proteins) distinguishe native cells (self) from foreign (non-self) The first 2 lines of defense agounst infection are the physical and chemical barners put in place by the body and the non-specific immune response (which includes phagocytes) Gif they won't enough to prevent infection, the specific immune response will be triggered. distinct Specific immune response has 2 kpo parts: Blymphocytes - humoral respenses. BT-lymphocytes - cell-mediated responses. cell-mediated response: Specific to the antigen 4 T-lymphocyles only respond to antigens which are presented on other cells, rather than antigens within body fluids. >what kind of cells will present antigens on their surface? transplant cells. cancer cells. Sphagocytes that have engulfed and hydrolysed a pathogen. 4virally infected body cells. 4 All of these cells are antigen presenting cells CAPC). There are 2 main types of T-lymphocytes: helper T-cells. Cytotoxic T-cells (killer T-cells). Fiday 9th December 2022 The role of T and B lymphocyte B- lymphocytes: produce antibodies, which are protein molecules specific to an antigen. when the antibodies bind to specific antigens on a pathogen, they get neutralised. antibodies are present in plasma, so B-lymphocytes are involved in 'humoral immunity. I-lymphocytes: have specific receptors on their plasma membranes, which are specific to antigens present on a body cell involved in cell-mediated immunity Cellular response of lymphocytes: there are millions of lymphocytes with different receptors antigens. for different pathogenic organisms. when a specific pathogen invades the body, the lymphocyte with the correct receptor has to be found. and activated. Cional selection = the contact and subsequent activation of the complementary receptor on a lymphocyte to the specific shape of an antigen. contact can be direct or indirect. Direct contact ⇒ when the lymphocyte comes across the pathogenic cells in the lymph nodes Indirect contact when the lymphocyte comes across an antigen-presenting cell which phagocurosed the pathogen. Lother immune cells, like macrophages, then secrete interleukins Ca type of cell- signalling molecule) Linterleukins specifically bind to the selected lymphocyte, causing it to divide by mitoss cloning cional expansion = mitotic division increasing the number of cells. 4 Clonal selection and clonal expansion take a long time >Activation of T-cells: La lymphocyte engulfs a bacterium with antigens on Surface Lymphocyte presents antigens on its surface → becomes antigen presenting cell (APC). APC binds to T-helper cell with complementary CD4 receptors (these will recognise the antigen). LT-helper cell is activated and dindes through mitosis clone of active Thelper an effect on the body clone Subsequent infections, giving us immunity → stored in lymph nodes. T-memory >The cloned T-cells: develop into memory cell that enable a rapid response to future infections by the same pathogen stimulate phagocytes to engulf pathogens through phagocytosis stimulate B-cells to divide and secrete their antibody. activate cyto-toxic T-cells (Tc cells). Monday 12th December 2022 > What is the humoral immune response ? B-lymphocytes and humoral immunity. 4 the involvement of antibodies, which are soluble in the blood and tissue fluid, in immunity. How does humoral immunity work? when a pathogen with antigens enters the blood, there will be one B-lymphocyte with a complementary. antibody on it's surface The antigen and antibody attach, and the antigen enters the B-lymphocyte by endocytosis, it then gets presented on its surface T-helper cells bind to the processed antigens and stimulate mitosis to form identical Cclonal selection) clones Some pathogens also produce toxins which also act gas antigens therefore, many different B-cells make clones to produce its own type of antibody (monoclonal antibody). In Each clone, one of 2 types of cells are produced: 1-Plasma cells: • secrete antibodies into blood plasma Lonly survive for a few days but produce around 2000 antibodies per second. immediate defense destroy antigen primary immune response. 2→ Memory cells: Glast longer (decade)) → long-term immunity.. do not produce antibodies directly circulate in blood and tissue fluid. Gensures a new infection is destroyed before it harms. secondary immune response. Saturday 10th December 2022 How do Cytotoxic T-cells (Killer T-cells) work? L Bacterium infects cell of host the cell presents antigens and becomes an APC T-killer cell with complementary receptor binds to APC. Cytotoxic T-cells divides, forming two clones: active and memory T-killer cells T-helper cells produce cytokinin which promotes mitosis Lactive T-killer cells bind to infected cells presenting Cytotoxic-T-cells antigens LiPerforin is produced, making holes in the memb- -rane, making it permeable to all substances. cell-lysis occurs due to water entering Phagocytes engulf the cell's content, preventing replication.