4 Immunity& Disease Flashcards
Immunity& Disease
Revision of Immunity Innate Immune System Adaptive Immune System Immune System Suppression Immune System Hyperactive Manipulation of Immune System
Why do you need to know?
Affects all patients
Infections common
Some patients more susceptible to infection
Some medical conditions caused directly by the immune system
What is Immunity?
Protection or defence against infections… Bacteria Virus Fungi Toxins Cancer
Immune System
Distinguishes self from non-self molecules
Activates multiple mechanisms to either eliminate or neutralise threat
2 main pathways
Innate
Adaptive
Defence against disease
Innate immunity
Defense mechansims present even before infection or activated in a non-specific way
Skin, mucous membranes
Phagocytic cells (neutrophils, macrophages), inflammation, fever
Adaptive immune reponse
Cell-mediated immunity
Humoral immunity
Non-specific defences
Non-specific defenses are designed to prevent infections by viruses and bacteria
These include
Intact skin
Mucus and Cilia
Skin
Outer layer of keratin – mechanical barrier
Dead skin cells constantly sloughed off
hard for invading bacteria to colonize
Sweat and oils contain anti-microbial chemicals
Mucous membranes
Normal flow of mucus washes bacteria and viruses off of mucus membranes
Cilia (hair-like projections on cells) – respiratory tract
Acid – stomach, vagina
Enzymes – saliva, eye
Chemical barriers
Proteins
Complement - works with other defence mechanisms of the body
Interferons - inhibit the replication of many viruses
Cellular defences - phagocytosis
Granulocytes
Neutrophils, eosinophils, basophils
Remove dead cells and micro-organisms
Attracted by an inflammatory response of damaged cells
Monocytes
macrophages
In tissues which serve as filters for trapping microbes
Macrophages live longer than granulocytes
Attracted by different stimuli and usually arrive at sites of invasion later than granulocytes
Stimulate specific immune response (‘antigen-presenting’)
Non-specific responses to infection
Macrophages release protein signals
interleukin-1 (IL-1) and interleukin-6 (IL-6)
Fever
Most bacteria grow optimally at temp below body temp
Pain, swelling, redness
Increasing capillary permeability, promoting blood flow, bringing more phagocytic cells
Acute-phase proteins released from liver
Bind to bacteria and activate complement proteins
Specific (adaptive) immunity
Relies on antigens
specific substances found in foreign microbes
Lymphocytes
Can travel swiftly around the body when carried along in the blood or lymph
Approx 2 x 10^12 lymphocytes in human body
Approx 1 % are in the bloodstream
Rest in lymphatic system
Lymphocytes
Produced in bone marrow
B-cells mature in bone marrow then concentrate in lymph nodes and spleen
T-cells mature in thymus
B and T-cells mature then circulate in the blood and lymph
Circulation ensures they come into contact with pathogens and each other
Lymphocytes
B-cells
Secrete antibodies
Humoral immunity
Recognise pathogens outside cells
T-cells
Do not recognise free antigen - only recognise antigen presented by major histocompatibility complex – class I (all cells) or class II (APC)
Directly attack invaders (cytotoxic, CD8+, MHC I)
Cell-mediated immunity
Recognise pathogens that have entered cells
Also help B-cells (helper cells, CD4+, MHC II)
T-cells
Cytotoxic
Seek out and destroy any antigens in the system, and destroy microbes “tagged” by antibodies
Some cytotoxic T-cells can recognize and destroy cancer cells
Variable region on T-cell receptor
Helper
Stimulate B-cells
Activate cytotoxic - cells and macrophages to attack infected cells
