Immunity Flashcards
Immunity
The ability of the host to fight against a disease/infection causing organism (pathogen) encountered by the immune system is termed as immunity
Name the two types of immunity
- Inborn / Innate / Gerneralised Immunity
- Acquired Immunity
Difference b/w vaccine and toxoid
Vaccine:
1. Provides lifetime immunity
2. Vaccines contain killed or attenuated disease-causing organisms
Toxoid:
1. 6 months immunity
2. Toxin is produced by the microorganism
Artificially acquired active and passive immunity
Active:
Antigens are introduced in vaccines; body produces antibodies and specialised lymphocytes
Passive:
Preformed antibodies in immune serum are introduced by injection
Blood cell formation
1. Early foetal development
2. Mid foetal development
3. Later foetal development
- mesenchyme of yolk sac
- liver and spleen
- bone marrow
Bone marrow function
- Gives rise to all lymphoid cells
- Maturation and proliferation of B-cells (B-Lymphocytes)
Thymus function
- Major action of thymus occurs during childhood
- Maturation and differentiation of T-cells (T-Lymphocytes)
Lymph nodes function
- Non-specific filtration of particulate matter
- Proliferation of B and T lymphocytes
Spleen function
- B-cells and T-cells multiply
- Removal of debris, particulate matter and aged/defective RBC- MALT, NALT, GALT, BALT
MALT: Mucosal Associated Lymphoid Tissue
NALT: Nasal
GALT: Gut
BALT: Bronchiole
Phagocytosis
Phagocytosis is a non-specific response. It is the process of engulfment and destruction of particles such as bacteria, allergens etc. by specific cells like macrophages and neutrophils
Inflammation
Inflammation is a protective and non-specific immune response which is elicited due to a tissue injury. Inflammation can be localised or systemic.
Inflammation- steps
- Tissue injury
- Swelling: Vasodilation of the capillaries around the area of tissue damage
- Redness: Increased amount of blood flow in the area
- Heat: Temperature raises locally in that specific region
- Pain: Permeability of the capillaries result in the escape of plasma into the surrounding region
- Plasma contains phagocytic cells, antibodies, and bactericidal agent
- Destruction of antigens and healing of tissue
Difference b/w B-cells and T-cells
B cells
1. maturation and differentiation in bone marrow
2. accounts for humoral immune response
T cells
1. maturation and differentiation in thymus
2. accounts for cell-mediated immune response
APCs
Antigen Presenting Cells
Macrophages and neutrophils
Destroy antigens by phagocytosis, non-specific immune response
Interferons
- Anti-viral in action
- Specific in nature
- Signaling proteins released by virus infected cells
- Interfere with viral replication
- Signal the neighbouring cells to increase their anti-viral defenses
Examples:
IFN-alpha and IFN-beta are secreted by virus infected cells
IFN-gamma is secreted by T-cells, NK cells and Macrophages
Antigens
- Foreign molecule that can trigger the immune system of the host organism in producing an antibody
- Most anitgens are either proteins or polysaccharides
- Lipids and nucleic acids become antigenic only when they combine with a protein or polysaccharide
Haptens
These are small molecules that can elicit an immune response only when attahed to a large, carrier molecule, like a protein
Antibodies
- Proteins (Gamma globulins)
- Specific in function
- Released by Plasma cells (B-cell)
- Forms Ag-Ab complex to facilitate the destruction of antigen
Effector mechanisms
- Agglutination
- Opsonisation
- Complement (specialised plasma proteins) mediated cell lysis
Number of binding sites in IgG, IgM, IgA, IgD, IgE
IgG, IgD, IgE: monomers–> 2 binding sites
IgM: pentamer–> 10 binding sites
IgA: dimer–> 4 binding sites
Percentage of total antibody in serum
IgG, IgM, IgA, IgD, IgE
IgG: 80%
IgM: 6%
IgA: 13% (monomer)
IgD: <1%
IgE: <1%
Fc receptor binds where in IgG and IgE
IgG- phagocytes
IgE- mast cells and basophils
Function of IgG
- Neutralization
- Agglutination
- Complement activation
- Opsonization
- Antibody-dependent cell-mediated cytotoxicity
Function of IgM
- Neutralization
- Agglutination
- Complement activation
- The monomer form serves as the B-receptor
Function of IgA
Secretory antibody
1. Neutralization
2. Trapping of pathogens in mucus
3. Present in tears, saliva, and colostrum
Function of IgD
B-cell receptor
Active against parasitic infections
Function of IgE
Activation of basophils and mast cells against parasites and allergens
Allergy
An oversensitive reaction by the immune system against a foreign particle (Allergen)
Clinical manifestations of an allergy
- Itching
- Swelling
- Redness
- Typical wheal and flare reaction on the skin
Treatment for allergic reaction
Administering anti-histamine drugs
Autoimmunity
- The condition where an individual produces antibodies against one’s own antigens
- The body loses its ability to differentiate between self and non-self antigens
Disease when there is autoimmune disorder related to
1. RBC antigen
2. Muscle antigen
3. Thyroid antigen
4. Antigens in joins
- Chronic anaemia
- Myasthenia gravis
- Hashimotto’s disease
- Rheumatoid arthritis
Immunodeficiency disorders
- SCID- Severe Combined Immuno-deficiency- T and B cells absent: congenital
- Di George’s Syndrome- lack of T-cells
- Agammaglobulinemia- lack of B-cells
- AIDS: Acquired Immunodeficiency Syndrome
