immunity

Pathogen

organism able to cause disease

antigen

any foreign substance in the immune system

eg. bacteria, viruses, fungi, parasites, foreign cells

MHC I

protein found on the surface of almost all body cells, enables the human immune system to achieve self recognition

MHC II

proteins on antigen-presenting cells that present foreign antigens to helper T cells, activating the adaptive immune response

Bacteria

single celled prokaryote that doesn't have a nucleus

relatively few types are pathogenic, bacteria infect a host to exploit food from the hosts body tissues

Fungi

eukaryotic organisms, reproduce through spores

secrete digestive enzymes that break down hosts tissue and cause disease

protozoa

single celled, eukaryotic microorganisms, can be free living or parasitic

multicellular parasites - endoparasites

live on tissue inside host - infect plants or animals

multicellular parasites - ectoparasites

live on outer surface of a host - infect plants or animals

vector

organism that transports a pathogen from one organism to another

prions

infectious misfolded proteins that contain no genetic material, cause disease by inducing normal proteins to misfold as well

Viruses

a non cellular, intracellular parasite

uses reverse transcriptase to reproduce it's own DNA/RNA, quickly reproducing virus

the outer layer of skin is dead, viruses must invade a living cell and breach first line of defence to reproduce

first line of defense

innate, non specific - prevent entry and development of pathogen into live tissue

first line of defense - physical barrier

entry of pathogen is impeded or prevented - intact skin, wax, hairs, thick bark, waxy surface

first line of defense - chemical barrier

inhibit the growth or development of pathogens or act to destroy them - stomach acid, lysozymes (tears), caffeine, tree sap

first line of defense - microbiological barrier

prevent the growth or colonization of pathogens by competing for nutrients or altering conditions - beneficial bacteria - gut, soil

second line of defense

innate, non specific - involves specialized cells and chemicals, creates inflammation and fever

natural killer cells

recognises a cell as non-self through a lack of MHC 1 marker on virus infected cells - destroys abnormal and virally infected cells by triggering apoptosis

apoptosis

targeted cell death

a cell is found as non-self and receives a death signal - perforin is released punching holes in the membrane and secreting granzymes that trigger apoptosis, killing the cell which will then be engulfed by a phagocyte

phagocytes

collective term for white blood cells that engulf pathogens in the second line of defence - will engulf anything with a foreign antigen

cytokins

small proteins that act as chemical messengers

neutrophills

most common phagocyte - engulfs and digests pathogens in second line of defence

macrophages

antigen presenting cell, engulfs pathogens, releases cytokins to coordinate an immune response

antigen presenting cell

macrophages and dendritic cells - specialized immune cells that engulf pathogens and digest their proteins into peptides - they are involved in linking the second to the third line of defence by displaying an antigen on an MHC 2 marker

dendritic cells

main antigen presenting cells - engulf pathogens

eosinophils

phagocytes that release toxic substances to destroy parasites and contribute to an allergic inflamation

complement response

20+ proteins produced in the liver - coat bacteria and mark for engulfment by phagocytes

activated when bound to PAMP'S or antibodies

• creates a membrane attack complex, creating lysis

• attracts phagocytes via chemotaxis (chemical gradient)

• pathogen is oponised, flagged for destruction

• trigger inflammation

interferons

signaling proteins released from virally infected cells, that help protect nearby cells from viral infection - inhibit protein synthesis

Mast Cells

immune cells full of vesticles containing histamine that is released when damaged

when histamine is released:

vasodilation of blood vessels - brining more blood to the area

increased permeability of blood vessels - increased leakyness allowing white blood cells and fluid containing immune agents to leave the blood and enter tissues

inflammation

pain, redness, heat and swelling - immediate response, triggered by cytokines, released by tissue when damage occurs, or when pathogens have entered the second line of defence

fever

regulated increase in body temperature about 36.5 due to macrophages release interlukins (lots of cytokines) in response to an infection

beneficial at slowing rate of bacterial replicatIon

third line of defence

adaptive, specific immune response, involving B cells, T cells, antibodies and memory cells

Cell Mediated Immune Response

the adaptive immune response producng specialized T cells, that destroy infected or abnormal cells after recognising specific antigens

Helper T cells

are activated when the T cell receptor binds to a specific antigen presented on an MHC 2 marker on an APC, dendritic or macrophage

when activated secrete cytokins that activate clonal expansion of the Helper T cells, and stimulates production of cytotoxic T and B cells

cytotoxic T cells

activated in lymph nodes by cytotoxic T helper cells, recognise MHC 1 marker on intracellular antigen displayed on cell, used to eliminate cells that are reproducing viruses, infected or abnormal by triggering apoptosis

Memory T cells

some activated cytotoxic T cells become memory T cells, that persist in the body allowing a faster and stronger response if the same pathogen reinfects the body

humoral immune response

adaptive response involving B cells producing antibodies against specific extracellular antigens

B cell activation

Helper T cell binds to a specific antigen displayed on MHC 2 marker, secreting cytokins that active B cells, triggering clonal expansion

B cell differentiation

process where activated B cells become specialized into either Plasma or Memory B cells

Plasma Cells

develop from B cells, produces antibodies against one specific antigen, produces quickly

B memory Cells

give active immunity, when reencounter same antigebm rapidly differenciate into plasma cells limiting antigens effect on the body

clonal expansion

clones of the same specific receptor to match the antigen

Lymphatic system

a network of lymph vessels that return excess tissue fluid to the bloodstream and supports immune response by stimulating adaptive immune response

primary lymphoid organ

bone marrow and thymus - where lymphocytes are produced and matured

T cells travel to the Thymus to mature

B cells mature in the Bone marrow

both produced in the bone marrow

secondary lymphoid organ

lymph nodes, tonsils, adenoids - where B and T cells encounter antigens and are activated and initiate an immune response

antibodies

Y shaped quaternary protein produced by plasma cells that binds to specific antigens to help eliminate the pathogen

Neutralization - of antibodies

binds to toxins and pathogen surface proteins, neutralising them and oponises pathogens so phagocytes can easily recognise and destroy it

Agglutination - of antibodies

binds to antigens on two seperate pathogens go form an antigen - antibody complex, immobilising the pathogen

antibody bound to pathogen triggers complement activation, activating a group of proteins in the blood to fight infection

immunological memory

memory of encounters of a lymphocyte with an antigen

primary immune response - memory cells are produced

secondary immune response - memory cells are activated, lymphocyte and antibody production occurs quicker and response is more intense and longer lasting

immunity

the ability of the body to fight off pathogens

active immunity

acquired immunity, every time your body produces antibodies as a direct response to an antigen, body must work to produce antibodies and memory cells

Natural - active immunity

from random exposure to the pathogen in a natural setting

artificial - active immunity

artificially coming into contact with pathogens, deliberately introduced first exposure to a pathogen - vaccine

Passive immunity

antibodies are transferred between individuals, no immunological memory gained, innate immunity

passive, no memory cells produced

Natural - passive immunity

antibodies transferred across the placenta and breast milk

artificial - passive immunity

occurs when a person recieves an injection of antibodies or snake antivenom

not antibiotics - must be ready made antibodies produced by someone else

vaccine

a substance containing antigen that triggers an immune response and immunological memory

herd immunity

most people being vaccinated so those who are immunocompromised are less likely to get infected - need 95% vaccinated for success

a higher percent of the population vaccinated means diseases are less likely to spread

immunocompromised people/ immunodeficiency

cannot be vaccinated, due to a weakened immune system

Primary - born with it, SCID, no immune system

Acquired - AIDS, HIV, destroys body's ability to produce helper T cells

Allergies

exaggerated responses to antigens called allergens in our environment, reaction occurs from the release of histamine by mast cells

Cancer

a group of diseases due to uncontrolled growth of cells, that multiplies and oncogenes (can turn normal cells cancerous)

Monoclonal Antibodies (mAb)

identical, lab grown antibodies produced from one clone of B cell

produced by stimulating production of B cells in mice by using an antigen

Chimeric mAb

contains a mixture of the components of both human and mice, designed to reduce reactions in humans

Humanised mAb

engineered to contain mostly human components, less likely to be rejected by humans

Conjugated mAb

chemically linked to another molecule (Drug, toxin) to deliver it specifically to a target cell to kill it

Bispecific mAb

artificially produced to have two different binding sites, allowing it to bind to a target and immune cell at the same time, brining them closer together

infectious disease

a disease caused by an agent that can be passed on from one organism to another, contagious

Zoonosis

a pathogen which can cross a species barrier, moving from one species to another, can only be transmitted from an animal with a back bone

epidemic

situation where many people n a region contract a specific disease over a short time

pandemic

situation where many people in a large geographical region contract a specific disease as it spreads over a relatively short period of time

endemic

a disease that is consistently present with a population in a particular region

incidence

rate of occurrence of a specific disease in a population in a specific period of time