Explain why multi-cellular organisms discriminate between self and non-self. Flashcards
What are the different types of leukocytes (3 types and their sub-types)?
Granulocytes: Basophils, eosinophils, neutrophils. (Involved in our inflammation responses, and produce the anti-clotting agent heparin)
Agranulocytes: Lymphocytes (B-cells, T-cells and natural killer cells (B and T cells can be further sub divided)) and monocytes (macrophages).
Megakarocytes: Platelets (Involved in blood clotting).
Neutrophilis and monocytes are phagocytes (phagocytes are the largest type of leukocyte, they engulf pathogens and destroy them).
https://en.wikipedia.org/wiki/White_blood_cell
good table summary
Describe the role of neutrophils?
Neutrophils make up the largest portion of leukocytes in the body, they circulate around the blood. When they could into contact with bacteria they will consume them, they are phagocytes. So they are particularly important in combating bacterial infections.
Describe the role of basophils?
Basophils make up the smallest amount of leukocytes in the body but can have a large response when activated. They detect invaders and produce antibodies. They also signal for other leukocytes to aid in the immune response.
Describe the role of Eosinophils?
Eosinophils target bacteria and parasites. They can kill the invader without knowing it. This is unlike other leukocytes. They trap the invader and are involved in allergic responses. They have also been shown to be involved in some organ formation and tissue repair.
Describe the role of Monocytes?
Monocytes are the biggest type of leukocytes in the body. They are macrophages that are phagocytes. Can be considered the back up to the neutrophils destroying the invaders that were not captured.
Describe the role of Lymphocytes?
Lymphocytes provide immunity against foreign bodies.They can be sub divided depending on the role they carry out. They make up about 20-30% of the circulating leukocytes but many more are stored in other tissues and glands.
T (thymus-dependent) cells, B (bone-marrow derived) cells, NK (natural killer) cells. The majority of the circulating lymphocytes are T cells.
B Cells- identifies bacteria that enters the body, then form antibodies that prevent the invaders function. Marks them so that other leukocytes (T-cells) can recognise them and destroy them. (antibody-mediated/ humoral immunity as it occur in the body fluid).
T Cells- are able to directly destroy the invaders body.
There are different types of T cells including cytotoxic, (cell-mediated immunity), Helper (stimulate the function of both T and B cells), suppressor (inhibit the activation of both T and B cells). Helper and suppressor T cells are also know as regulatory T cells as they control the sensitivity of the immune response.
Natural killer cells: described as immunological survelliance as they continously circulate the peripheral tissues. They attak foriegn cells cancerous cell and viruses infected cells.
Describe some key properties of Leukocytes
Leukocytes are specialised cells that can defend our bodies from pathogens (infectious disease and foreign invaders). All leukocytes originate from cells in the bone marrow called hematopoietic stem cells which are multipotent. They are able to differentiate into a variety of different cells with different functions. Leukocytes are found throughout the body, including the blood and lymphatic system. All leukocytes have nuclei, which distinguishes them from the other blood cells, the anucleated red blood cells (RBCs) and platelets.They are amoeba like cells that are able to move independently. they are able to move against the flow of blood and through our capillaries walls into tissues in a process called diapedesis. They make up 1% of the total blood volume.
An increase in the number of leukocytes over the upper limits is called leukocytosis. It is normal when it is part of healthy immune responses, which happen frequently. It is occasionally abnormal, when it is neoplastic or autoimmune in origin. A decrease below the lower limit is called leukopenia. It weakens the immune system.
How are granulocytes and agranulocytes distinct?
They can be distinguised from one another via their nucleus. Granulocytes have a lobed versus round, that is, polymorphonuclear versus mononuclear) and by their cytoplasm granules (present or absent, or more precisely, visible on light microscopy or not thus visible)
What is the innate immune (non-specific) response?
Granulocytes are involved in the innate immune response. Skin acts a barrier against pathogens entering the body, mucus in the respiratory system trap pathogen and cilia waft them to the stomach. The partial cells in the stomach secrete hydrochloric acid to kill most pathogens. Fever and inflammation is part of the innate response. This type of immune response occur immediately. Lysosomes is found in the tears and saliva that breaks down the cell membranes of pathogens.
Includes: Physical barrier, mucus membrane, fluid secretions, phagocytes and neutrophils, inflammation and fever. We are born with these responses. Therefore they act as the primary defence mechanism. It is non-specific e.g does not attack a specif type of pathogen.
Cells known as macrophages also play a large role in innate immunity. Macrophages recognize bacterial or viral components such as lipopolysaccharide (LPS) or double-stranded RNA (dsRNA), via special receptors known as Toll-like receptors (TLRs). TLR activation cause macrophages to secrete cytokines (small molecules involved in cell signaling and attraction), as well as to phagocytose the infected cells. The innate immune system is required to activate our adaptive immune system.
What is the adaptive/aquired or specific immune response?
Lymphocytes (agranulocytes) are involved the the adaptive immune response. This type of immune response takes several days to occur. It involves cell-mediated (T-cells) and antibody-mediated (B-cells) immune response.
Cell-mediated: our defence against abnormal cells and pathogens inside cells.
Antibody-mediated/ humoral immunity: our defence against antigens and pathogens in body fluids.
Our body learns and develops these responses.
Types of acquired immunity:
Passive immunity:
Induced passive is when antibodies are given via an injecttion
Natural passive is when antibodies are pass on via a mother to child via placenta or breast milk.
Active immunity:
Naturally acquired development after exposure to antigens e.g infection from environment.
Induced active development after exposure to antigens e.g through vaccines.
Acquired immunity is:
Specific to particular antigens due to their individual structures.
Versatile thousands of different leukocytes and when one is activated thousands more of the same is synthesised clones to aid in the immune response. So has the potential to combat millions of different pathogens.
Memory the immune system remember antigens it encounters, so the second response to the same antigen is stronger quicker and longer. By maintain some memory cells from the first invasion of pathogen.
Tolerance the immune response does not act against all pathogens and has a tolerance.
Phagocytes are exposed to the antigen, then T cells are activated attack antigen and stimulate activation of B cells. Mature B cells produce antibodies that are distributed into the blood stream and attack the antigens.
What do Lymphocytes (T-cells)?
Are part of the cell mediated response. The differentiate into killer T cells that recognise foreign antigens and destroy pathogens. Helper T cells that release chemicals and assist maturation of the cell, memory T cells which also help to protect from re-infection and suppressor T cells that which regulate and suppress the immune system.
What is the role of Megakarocytes?
They break apart to form platelets that are made solely of cytoplasm they aggregate around a cut in a vessel forming a patch. They release other chemicals that stimulate the other cells in the immune response and blood clotting responses.
Antibodies (Immunoglobulins) Ig.
What are the 5 different types of Ig?
IgD found on the surface on B cells can bind to antigens in the extracellular fluid. Little understood about these.
IgA found in glandular secretions like saliva, tears, mucus. Found in mother’s milk.
IgM react first have a starfish strcture
IgG react second and have main functions they are versitile
IgE react to cause inflammation
Each Ig have a slightly different function/mechanism in the immune response. They are proteins of the immune response.
What is the basic structure of an Ig?
They have four polypeptide sub-units. They form disulphide bonds (convalent bonds). Producing a Y like shape. Two of these chains are heavy chains and the others are light chains (they are smaller than the heavy chains). There is a region constant region and a variable region.
Variable region: Contain specific sequence of amino acids that can bind to the antigen that it was designed for. This region contains the cleft that blinds to the antigen. Most antibodies have two. The antigen binding site binds to the epitope of the antigen. This blinding then forms the antigen-antibody complex that elitists a response.
Constant region: Determines the type of class of Ig and the mechanism which uses to fight/destroy the pathogen.
Antibodies can either be attached to immune cells or float freely in the blood. Antibodies and antigens bind together via hydrogen bonds.
What are the different MHC proteins
MHC I: pick up small peptides from the surrounding cytoplasm and takes them to the cell surface. If recognised as foreign by T cells they stimulate immune response.
MHC II:
CD: are markers on T-cells that aid binding of the T cell to the MHC on the infected cell. The type of CD determines which MHC it can bind to.
CD8: found on cyctoxic T cells and suppressor T Cells and memory Tc cellsbind to MHC I. Tc cells response is much quicker that Ts which means the Ts cells action occur later and puts the brakes on the immune response once it is near completion.
CD4: found on helper T-cells, memory Th-cells and bind to MHC II
Costimulation when the T cell binds to a secondary site determines if the T cell can become activated which prevents mistakenly attacking a self cell.
