| what are lysosomes? | vesicles containing enzymes
they can fuse with phagocytes to form a phagolysosome
they are made by the Golgi apparatus |
| what are interferons? | proteins
involved in cell communication to prevent infection
they are specific to viruses |
| how do interferons prevent infection? | prevent viral replication
they activate specific immune response cells
promote inflammation |
| define specific immune response | the body's response to the presence of foreign antigens causing antibodies to form |
| what is an antigen? | proteins or polysaccharides found on the surface of a cell
must be identified as foreign
cause the formation of antibodies |
| structure of an antibody | they are attached to B-cells
made up of 4 polypeptide chains
disulphide bridges hold them together
they have active sites specific to the antigen
the constant region allows binding to receptors
the variable region is complementary to the antigen |
| function of an antibody | agglutination
neutralises toxins
block cell surface receptors
stimulate the production of histamines |
| describe the process of antigen presentation by phagocytes | phagocytosis of the pathogen has occurred
the phagocyte sticks the antigen on its surface by its MHC
this activates the specific immune response cells |
| what is the role of a neutrophil in the immune system? | they are part of the primary immune defence system
they block, disable, digest and ward off invading pathogens |
| what is the role of a monocyte in the immune system? | immature macrophages
they engulf and digest pathogens |
| what is the role of T-cells in the immune system? | T-helper cells support B-cells in the production of antibodies
T-killer cells attack cells that have been infected
T-memory cells remember the specific antigen |
| structure of viruses | strands of RNA or DNA
attachment proteins (gp120)
capsid
protein-lipid membrane or viral envelope
reverse transcriptase, intergrase, protease |
| cell mediaTed response | the host cell becomes an APC by displaying antigens on its MHC
T killer binds to the APC with CD4+ receptors
cytokines secreted by T helper stimulate T killer to divide by mitosis
T killer divides forming active T killer and T memory cells
active T killer cells bind to the APC and secretes chemicals which causes pores to form in the cell membrane and the cell bursts and dies |
| post trancriptional modifications of mRNA | RNA splicing
a gene is transcribed resulting in pre-mRNA
all introns and some exons are removed
the remaining genes are joined back up by spliceososomes
the same exons can be joined in many ways to produce different versions of mature functional RNA |
| the major routes for pathogens into the body | inhaled
ingested
cuts in the skin |
| physical barriers to infection | skin and gut flora
the skin
stomach acid
lysozymes in tears |
| how does the skin prevent infection? | skin is made of the hard substance keratin
hard to diffuse into or penetrate |
| how does stomach acid help prevent infection? | hydrochloric acid
the conditions are too acidic for bacteria to survive |
| how do skin and gut flora help prevent infection? | natural bacteria found on the surface of the skin and gut
out-competes other pathogens for space, food and moisture |
| what are lysozymes? | enzymes that are found in lysosomes
examples include carbohydrase, protease and lipase
they are commonly found in mucus, tears and other fluids
they break down the bacterial cell walls by attacking the peptidoglycan through hydrolysis |
| outline the process of phagocytosis | phagocyte attaches to the microbe
it is engulfed into a vacuole called a phagosome
phagocyte and lysosome fuse to form a phagolysosome
the microbe is killed and digested by lysozymes released by the lysosome |
| describe the series of events involved in the non-specific response | damaged cells send out chemicals causing neutrophils to accumulate at the site in the capillary
mast cells in the tissue fluid are at the site
mast cell release histamines
histamines cause vasodilation of local arterioles causing local redness and heat
they also make the capillary walls leaky because the endothelial cells part slightly
this allows plasma, antibodies and neutrophils to enter and destroy the bacteria
this will increase tissue fluid in the capillary causing oedema (swelling) |
| how does inflammation occur? | histamines cause vasodilation of local arterioles
this causes local redness and heat
histamines also separate the endothelial cells
this allows more tissue fluid to enter the arterioles causing oedma |
| why are theses series of events termed non-specific? | because the system does not involve the production of antibodies complementary to the antigen on the microbe |
| what is the role of B-cells in the immune system? | B-effector: forms plasma cells
B-memory: they can record the specific antibodies needed should a second infection reappear |
| how does TB cause infection? | caused by mycobacterium tuberculosis
the bacteria is inhaled from the air of an infected person and lodges in the lungs
TB is usually latent until the immune system is weak
active TB will slowly destroy the lung tissue leading to breathing problems, coughing, weight loss and fever
TB bacterium can spread through the body in the tissue fluid or lymphatic system |
| T helper activation | the bacteria is engulfed by a macrophage
the macrophage displays antigens on its MHC
the macrophage acts as an APC
T helper cell binds to the macrophage APC by CD4 receptor
this activates the T-helper cell to divide by mitosis to form T memory cells and active T helper cells |
| process of the humoral response | T-helper cell activation has occurred
B-cells engulf the pathogen, digest it and present its antigen on its surface by the immunoglobulin/antibody
it becomes an APC
active T-helper cells bind to the APC releasing cytokines
cytokines cause them to divide into B-effector and B-memory cells |
| what is the MHC? | major histocompatability complexes
a group of genes that code for proteins
found on the surface of cells
help the immune system recognise foreign substances |
| B effector stage | humoral response
the B effector cells differentiate into plasma cells
plasma cells synthesise antibodies |
| how do antibodies destroy pathogens? | agglutination
neutralising toxins
block receptors
stimulate the production of histatmines
lysis
precipitation |
| what is HIV? | human immunodeficiency virus
destroys T-helper cells leading to AIDS
flu-like symptoms like fever, tiredness and headaches
a person is HIV positive when HIV antibodies are present in the blood |
| differences between bacteria and viruses | bacteria has no capsid
viruses have no pili, flagellum, cytoplasm, peptidoglycan cell wall, mesosome, ribosomes, plasmid, nucleoid
bacteria are bigger
viruses need a host cell to replicate
bacteria are prokaryotes
bacteria only have DNA whilst viruses can have both RNA and DNA |
| what is an APC? | antigen presenting cell
displays foreign antigens by the MHC on their surfaces for T cells to recognise |
| similarities between bacteria and viruses | both cause infection
both are not eukaryotes
both have enzymes |
| structure of bacteria | mesosomes
ribosomes
nucleoid
cell wall
circular DNA
plasmid
flagella
pili
cytoplasm |
| how can the non specific response be triggered? | the presence of antigens and their chemicals released from a foreign cell |
| T-cells | T-lymphocyte
three types: T-helper cells (naïve/active), T-memory cells, T-killer cells
have CD4 receptors on their surface
they mature in the thymus gland |
| what are Lymphoctes? | T-cells and B-cells
type of white blood cell found in the lymph
B-cells produce antibodies
T-cells provide immunity and also destroy foreign cells |
| what is the role of platelets in the immune system? | healing
first responder when a foreign particle enters the bloodstream |
| why does agglutination destroy pathogens? | brings microbes closer together so phagocytosis is easier |
| B-cells | B-lymphocytes
they are covered in immunoglobulins/antibodies
two types: B-effector and B memory
they mature in the bone marrow |
| why does stimulating the production of histamines help destroy pathogens? | allows an inflammatory response to occur |
| what are the stages of the humoral response? | T helper activation
B effector stage |
| how does precipitation help antibodies destroy pathogens? | soluble toxins are made insoluble |
| foreign cells | microbes, pathogens, viruses, bacteria
cells/particles that are not recognised as our own |
| give the names of blood cells involved in the non-specific immune response | neutrophils, mast cells, monocytes/macrophages, |
