Immunity Flashcards
Immunity
The state of being resistance to injury, invading pathogens and foreign substances through defensive mechanisms in the body is known as immunity
Immune responses in animals can be divided into two types
• Innate immunity
• Acquired immunity (Adaptive immunity)
Innate immunity
Is also known as non specific defense
Found in both vertebrates and invertebrates
2 types known as external defense and internal defense
External/ Barrier defenses
Considered as the 1st line of defense preventing the entry of pathogens from outside
3 main external defenses
skin
Mucous membrane
Secretions by various organs
4 major internal defenses
Phagocytic cells
Natural killer cells
Antimicrobial proteins
Inflammatory responses
2 types of antimicrobial proteins
Interferons and Complement proteins
Signs and symptoms of inflammation are
redness, heat, swelling and pain
Interferons and complement proteins
Interferons are proteins secreted by virus-infected cells which protect uninfected cells from viral infection by interfering with viral replication.
Complement proteins are a group of proteins which are normally inactive in plasma and plasma membranes. Promotes phagocytosis and inflammatory responses.
Pus
It is a fluid rich in dead phagocytes, dead pathogens and cell debris from the damaged tissue
Phagocytes
Phagocytes are a type of white blood cell that use phagocytosis to engulf bacteria, foreign particles, and dying cells to protect the body
Neutrophils and macrophages
Differences between macrophages and neutrophils
Macrophages are larger and more potent
Types of white blood cells
Types of white blood cells are granulocytes (neutrophils, eosinophils, and basophils), monocytes, and lymphocytes (T cells and B cells)
Acquired immunity shows
Specificity for particular foreign molecules
Recognition of animals own molecules from non-self molecules
memory for most previously encountered pathogens
Maturation sites of B and T lymphocytes
B lymphocytes are matured in the red bone marrow while T lymphocytes are matured in the thymus
Antigen
An antigen is a substance that has the ability to stimulate an immune response through T and B lymphocytes and to react with the specific cells or antibodies that is resulted from the stimulate immune response
B and T lymphocytes are produced in the
Red bone marrow
Examples for antigens
Viral proteins, bacterial toxins, bacterial structures, structural components of incompatible blood cells and transplanted tissues and cells
Epitope
An epitope is a small accessible portion of the antigen which binds to a specific antigen receptor of a T lymphocyte or B lymphocyte
Antibodies
Antibodies are proteins secreted by plasma cells (differentiated B lymphocytes) in response to specific antigens; the antibody binds with that antigen to neutralize, inhibit or destroy it.
Antibody-antigen complexes can activate complement system and phagocytosis to destroy the pathogen. Antibodies are also called as immunoglobulins
Interferons
Interferons are proteins secreted by virus-infected body cells that protect uninfected host cells from viral infections by interfering with the viral replication
Signalling molecules upon inflammation
Histamine (secreted by mastcells) and cytokines (by macrophages)
Phagocytes
Macrophages and neutrophills
Types of adaptive immunity
Cell mediated immunity
Humoral (antibody mediated) immunity
Cells involved in cell mediated immunity
Carried out by T cells
Cytotoxic T cells
Helper T cells
Memory T cells
What are effector cells and memory cells
Effector cells fight against the infection (cytotoxic and helper) while memory cells maintains an immunological memory about the infection (memory T cells)
Types of B lymphocytes involved in humoral immune responses
Plasma cells which produce antibodies
Memory B cells
Antigen presenting cells
Macrophages, dendritic cells and B cells
Steps followed during adaptive immunity
- Recognition of the antigen by B and T lymphocytes resulting in the activation (sensitization) of B and T lymphocytes
- Proliferation and differentiation into effector cells.
- Elimination of invaders
- Provide immunological memory
Active immunity
Immunity developed within the body due to the activation of B and T lymphocytes after a natural or an artificial infection (vaccination)
Passive immunity
Short term immunity developed within the body due to transfer of antibodies artificially or from mother’s blood to the fetus and through colostrum and breastmilk through breast feeding.
Allergens
Antigens capable of inducing a hypersensitive reactions in some persons.
Most allergens stimulate plasma cells which produce antibodies specific to the antigen.
When the allergen enter the body later, it binds with the antibody and stimulates the release of histamine and other inflammatory chemicals.
Allergies
Exaggerated responses of the body due to certain antigens (allergens)
Autoimmune disease
Resulted due to the sensitisation of immune system against self molecules
E.g; Autoimmune diseases
Type-1 Diabetes mellitus
Multiple sclerosis
Rheumotoid arthritis
Methods of attacking self tissues
By producing antibodies
By activation of cytotoxic T cells
Type-1 Diabetes mellitus
Resulted due to the activation of cytotoxic T cells destroying beta cells producing insulin hormone.
Multiple sclerosis
Cytotoxic T cells attack and destroy myelin sheath (Schuwann cells) around neurones affecting the transmission of nerve impulses.
Rheumatoid arthritis
Antibodies are produced against tissues surrounding the joints resulting in the erosion of the joint cartilage, bones and swelling of joints.
Immunodeficiency disease
Disorder in which responses of the immune system to antigens are defective or absent.
Secretions giving acidity to the skin
Secretions of sweat and sebaceous glands of the skin
Acquired immunity
Acquired immunity is the ability of the body to defend itself against invading foreign agents (e.g. pathogens) through specific defense responses mediated by diverse T lymphocytes and B lymphocytes.
Places where mucous membrane can be found
Lining of nasal tract
Digestive tract
Urinary tract
Reproductive tract
Secretions involved in external defences
Tears, saliva, mucus, perspirations of sweat, gastric juice and sebum (oil secreted by sebaceous glands)
Complement proteins
Normally inactive proteins in the blood plasma and plasma membrane. When they are activated by different substances present on the surface of microbes, a cascade of biochemical reactions occurs which lead to lysis of invaded cells. They also promote phagocytosis and inflammatory responses.
Main types of immunodeficiency
Diseases
Inborn immunodeficiency
Acquired immunodeficiency
Inflammatory response
Innate immune defence response in the body to tissue damage triggered by microbial infections or injury of the tissue
Antigen receptors
Specific protein receptors which have the ability to recognise specific foreign invasions.
