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
How do T-cells recognise an invader
Detect antigen – protein marker on cell surface
(Epitope = fragment of antigen)
If an antigen (“not self”) protein is encountered by a macrophage, it will bring the protein to a helper T-cell for identification.
If the helper T-cell recognizes the protein as “not self,” it will launch an immune response.
Signalling immune response
Helper T-cells (CD4+) stimulated by antigen cytokines to stimulate B-cell division
HIV destroys helper T-cells so immune response diminished
B-cells
Produce antibodies
Glycoproteins
Specific, hypervariable region
Different subtypes IgG, IgM, IgA, IgE, IgD
Opsonisation, bind and block (agglutinate), stimulate complement
Bind to antigen on cell or free plasma cells more antibody
Or become memory cells - remain ready to divide rapidly if an invasion occurs again
Immune System
Vital for survival but can be a double-edged sword
Immunodeficiency – prone to infections
Overactive immune system- hypersensitivity reactions
Failure to recognise self- autoimmune diseases
The Immune System
Deficient Chemotherapy / Drugs HIV Splenectomy Bone Marrow dysfunction
Hyperactive
Allergy (Hypersensitivity)
Auto-immunity
Overreaction to Pathogen
Immunodeficiency
Drugs
Chemotherapy
Immunosuppressive Medication
Splenectomy
Bone Marrow Dysfunction
Immunodeficiency
HIV – Human Immunodeficiency Virus
- Retrovirus
- Infects CD4+ T cells
- causes AIDS (Acquired Immunodeficiency Syndrome)
Stages of progression : Infection, Latency, AIDS
AIDS - decline in CD4+ T-cells, opportunistic infections
Immunodeficiency
Important to know if a patient is immunosupressed
More prone to infection
Significantly alter the immune response of the patient to infection
Causes of secondary immunodeficiency
Malnutrition Burns Uremia Diabetes mellitus Immunotoxic medications Self-medication of recreational drugs and alcohol AIDS
Hyperactive
Hypersensitivity
Excessive immune reaction against harmless antigen.
Type 1 – Type 4 – based on mechanism.
Type 1 – Anaphylaxis/Allergy
e.g. Asthma, Rhinitis (Hay fever), Peanut allergy.
- Sensitization first step.
Over reaction to pathogen
Systemic Inflammatory Response Syndrome
Autoimmunity
failure of an organism in recognizing its own constituent parts as self
leading to an immune response against its own cells and tissues
Normally display “self tolerance”
Self reactive lymphocytes
deleted centrally
suppressed in periphery
Autoimmune Diseases
Type 1 Diabetes Mellitus
Coeliac Disease
Multiple Sclerosis
Hashimoto’s Thyroiditis
Manipulation of Immune System
Suppress Immune system
Organ transplant
- increased susceptibility to infection
Cancer – Immunotherapy
Vaccination
Vaccination
Active Immunity
Stimulate own immune system to elicit adaptive immune response, prevent future infection.
Success depends on Herd Immunity
Vaccination
Live (Attenuated) Vaccines - live, weakened pathogen
e.g. MMR
Inactivated Vaccines - inactivated, part of pathogen
e.g. Hepatitis B
Toxoid - bacterial toxin
e.g. Diptheria
Conjugated - antigen linked to protein carrier
e.g. Pneumococcal
