Immunity Flashcards
Define immunity
Immunity is the ability of an organism to resist disease by identifying and destroying pathogens.
Explain the types f immunity
Innate Immunity (Non-specific): Provides immediate defense against infection and is not specific to particular pathogens.
Adaptive Immunity (Specific): Develops more slowly and provides specific responses to pathogens, including memory for future responses.
Explain the physical barrier in innate immunity
Skin and mucous membranes act as a first line of defense by physically blocking pathogens from entering the body.
Explain the chemical barrier in innate immunity
Lysozymes: Enzymes found in tears, saliva, and mucus that can break down bacterial cell walls.
Stomach Acid: Hydrochloric acid in the stomach kills many ingested pathogens.
Explain the 4 cellular defense in innate immunity
Phagocytes: Cells that engulf and digest pathogens.
Neutrophils: The most abundant white blood cells that rapidly respond to infection.
Macrophages: Large phagocytic cells that engulf and digest pathogens and dead cells.
Natural Killer (NK) Cells: Destroy infected or cancerous cells by inducing apoptosis.(programed call death)
Explain the process of inflammatory response
Injury/Pathogen Entry: Pathogens enter through a cut or injury.
Release of Chemical Signals: Damaged cells release histamines and other chemicals.
Increased Blood Flow: Blood vessels dilate, causing redness and heat.
Increased Permeability: Blood vessels become more permeable, allowing immune cells and fluids to enter the tissue, causing swelling.
Phagocyte Recruitment: Phagocytes move to the site of infection to engulf pathogens.
Fever: Elevated body temperature helps inhibit pathogen growth and enhances immune cell function.
What are the antimicrobial protein involved in innate immunity
Interferons: Proteins released by virus-infected cells to help protect neighboring cells from viral infection.
Complement System: A group of proteins that enhance immune responses by promoting phagocytosis, inflammation, and cell lysis.
what is under adaptive immunity?
self and non-self recognition
What are the 2 main components involved in the adaptive immunity?
Lymphocytes: White blood cells involved in adaptive immunity, including B cells and T cells.
Antigens: Molecules that trigger an immune response.
What are the components involved in humoral immune response?
B Cells: Lymphocytes that produce antibodies.
Plasma Cells: Differentiated B cells that secrete large quantities of antibodies.
Memory B Cells: Long-lived cells that quickly respond to future exposures to the same antigen.
Explain the process of humoral immune response?
i. Antigen presenting cell @ APC (dendritic cell / macrophage / B cell)
phagocytizes pathogen and degrades it.
ii. Fragment of foreign antigen binds to the class II MHC protein forming MHC-antigen complex and displayed on the surface of APC
iii. TH cell with its antigen receptor and accessory protein, CD4 binds to the complex of APC
iv. APC releases interleukin 1 (IL-
to activate T_{H} cell
v. Activated T_{H} cell releases IL-2
vi. T_{H} cell proliferates producing activated T_{H} cells and memory T_{H} cells
vii. Once antigens are bound to B cell receptor (antibody) in the B cell membrane, the B cell displays those antigens that bound to the class 11 MHC molecule on the surface of it’s plasma membrane
viii. Activated T_{H} bind to the sensitized B cell
ix. Activated T_{H} cell will release IL-2 that co-stimulate the sensitized B cell and trigger its activation..
x. The activated B cell then proliferates or divides mitotically, producing memory B cells and plasma cells (effector cells).
xi. Plasma cells secretes antibodies.
xii. Antibody-antigen interaction occurs.
xiii. Triggers processes leading to pathogen destruction
xiv. Memory B cells are long-lived cells that can give rise to effector cells if the same antigen is encountered later in life
What are the components involved in cell mediated immunity
T Cells: Lymphocytes involved in directly attacking infected cells.
Helper T Cells (Th): Activate B cells and cytotoxic T cells.
Cytotoxic T Cells (Tc): Destroy infected cells by inducing apoptosis.
Regulatory T Cells (Treg): Help modulate immune responses and prevent autoimmunity.
Memory T Cells: Long-lived cells that respond to future exposures to the same antigen.
how specific immunity is aquired by cell mediated response
Infected cells, cancerous cells or leucocytes which have phagocytosed foreign material become antigen presenting cells (APC)
APC displays fragments of antigens on their cell surface membranes via MHC( MHC stands for Major Histocompatibility Complex. It’s a set of molecules found on the surfaces of cells that are essential for the immune system to recognize foreign substancesmolecules in their membranes).
When a helper T-cell (T_{H}) encounters and recognises the MHC-antigen complex T_{H} is stimulated to divide rapidly and produce activated TH cells and memory cells.
T_{H} cells have CD4 proteins on their membranes which bind with the MHC molecule on the APC.
interlukein 1 secreted by apc activates helper cell to secrete il2.
Activated T_{H} cells secrete cytokines that promote the activation of cytotoxic T-cells
(T_{C}) Tc cells have CD8 surface proteins that bind to the target cells, which are infected body cells or cancerous cells.
Activated T_{C} cells release perforin and proteolytic enzymes.
Perforin makes pores in the target cell membranes
while the proteolytic enzymes cause the death of the target cell.
After destroying the target cells, the T_{c} cells can go on to attack other infected cells.
explain the function of plasma cells and memory cells
Plasma cells secrete antibodies specific for the antigen that stimulated the activation of the B-lymphocytes.
Each plasma cell produces and secretes about 2000 antibody molecules per second.
The life span of the plasma cell is 4-5 days.
Memory cells are long-lived and are capable of rapid proliferation and differentiation when they encounter the same antigen in subsequent infections.
Memory cells responsible for rapid and pronounced secondary response which is the reason why individual rarely develop the symptoms of a disease more than
once.
Explain antigen
-Antigens are the molecules usually proteins, polysaccharides or glycoproteins
-carried on the surface of cells that cause antibody formation.
-All cells have antigen markers in their cell surface membranes
- but the body can distinguish between its own antigens (self) from foreign antigens (non-self).
Explain about antibidy
-Antibody is a specific protein (immunoglobulin)
- that recognises and binds to specific antigens
Antibodies either neutralise the antigen or tag cells that are antigenic.
Explain about epitope
These antigenic determinants are specific sequences of amino acids that confer a specific shape to the antigen molecule,which is then recognised by an antibody or T-cell receptor. An antigen may have several different epitopes on its surface.As a result, different antibodies may bind to a single antigen.
Explain about major histocompatibility complex
A set of closely-linked genes which code for a set of proteins (antigen markers) found on the surface of cells.
MHC Class I antigens are carried by most nucleated cells and are Important in self /non-self recognition.
MHC Class II antigens are mostly found on B-cells, macrophages and some T-cells.
MHC Class III proteins are components of the complement system.
