WEEK 7 - IMMUNE SYSTEM Flashcards
What does the immune system include and what does it carry out?
The immune system includes the cells and tissues that carry out immune responses (lymphatic system, immune cells- white blood cells)
NAME AND DESCRIBE THE 2 TYPES OF IMMUNITY
Innate immunity:
Non specific
Rapidly responds
Two ‘lines of defense’
Adaptive immunity
Specific
Memory
Acquired
Components of the innate immune system
First line (External)
Skin, Mucous membranes, Hairs, Cilia, Body fluids contain enzymes to destroy microbes and washes surfaces, Sebum, Excretions
Second line (Internal)
Granulocytes (neutrophils, eosinophils, basophils), Macrophages, NK cells
Components of the adaptive immune system
T cells – cytotoxic or helper
B cells – memory or plasma cells
Antigen presenting cells
INFLAMMATION
Symptoms of inflammation: Redness, Pain, Heat, Swelling
3 Stages of inflammation: Vasodilation, Emigration of phagocytes and Tissue repair
FEVER
Increased body temperature via changing the ’set point’ in the hypothalamus
Increased temperature can boost the effects of the immune/regenerative cells
Innate immunity – cellular mediators
Phagocytosis
Recognise patterns on a pathogens (e.g. LPS, free ds-DNA) and engulf in order to destroy
Direct cell killing (NK cell)
Recognise infected or cancerous cells and release substances to kill the cell
Antigens
Entire organisms or parts (epitopes) may act as antigens.
Identify self from non-self – each of us has our own specific antigen.
T and B cells have millions of different receptor/antibody combinations – specificity.
MHC (class I) – present self/endogenous antigens to patrolling immune cells
MHC (class II) – can present exogenous antigens. Present on APCs (macrophages, B cells, dendritic cells)
Adaptive immunity – T helper cells
T lymphocytes - cells that have special T cell receptors (TCR) – unique.
The regulators of adaptive immunity – co-stimulation
T helper cells express the CD4 protein and will bind to antigens presented on MHC II containing APCs. This activates the T helper cell.
Once activated T cells undergo clonal selection
Memory cells hold a memory of that antigen in case of future exposure
Adaptive immunity – antibody mediated
B lymphocytes – express B cell receptor (membrane bound antibodies) – unique,
Q). Effective against pathogens present in extracellular fluids (humours) – Why?
A). antibodies produced by B cells cause the destruction of extracellular microorganisms and prevent the spread of intracellular infections
B cell recognises antigen it is specific for and engulfs and processes it to present to T helper cell.
Specific T cell needed for co-stimulation.
Clonal selection of the activated B cell. Differentiation to plasma cells (antibody production) or memory B cells.
Antibodies bind to the antigen resulting in inactivation and marking them for destruction by phagocytes.
Adaptive immunity – cell mediated
Cytotoxic T cells express CD8 membrane protein and unique TCR.
Q). Effective against intracellular pathogens – Why?
A). Peptides from intracellular pathogens that multiply in the cytoplasm are carried to the cell surface by MHC class I molecules and presented to CD8 T cells. These differentiate into cytotoxic T cells that kill infected target cells.
Recognise and bind with MHC I antigen complexes
Co-stimulation by helper T cells required for activation and killing of infected cells and clonal expansion.
Active cytotoxic T cells can kill infected cells and memory cytotoxic T cells await re-infection
