immunology mw%% (+ Flashcards
What are the first line of defense?
Physical Barrier:
- Skin
- Mucos.
What are the 3 generic differences between adaptive and innate immune system?
- Specificity.
- Antibody production.
- Memory
What are the major cells involved in innate and adaptive immune system?
- Innate: Phagocytes (macrophage, neutrophils), natural killer cells: NK cells play a major role in the host-rejection of both tumours and virally infected cells.
- Adaptive: lymphocytes.
Describe the process of phagocytosis?
- Adherence
- ingestion
- formation of phagosome
- fusion with a lysomes to form a phagolysosomes
- digestion
- formation of residual body containing indegistable material and then discharge.
Where is the origin of macrophages and what is their funcion?
- Made in bone marrow and are called monocytes and then macrophages in the tissues.
- Function is redness and recruitment and phagocytosis.
Function of natural killer cells?
- Found in spleen (blood filter) and blood
- cause the cell to commit suicide by making a hole then releasing enzymes and chemicals contained within granule.
Eosinophil
- Help combat parasitic infections.
- Involved in allergy and asthma.
- Granules contain many enzymes.
Neutrophil
- Most abundant WBC
- Phagocytosis
What is the function of mast cells?
- On encountering a parasite the mast cell dumps all it’s contents onto the parasite to kill it.
- The contents of the mast cell can also cause an allergic reaction in the host which if it is severe enough can cause anaphylactic shock.
- Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death.
Basophil
- Least common of granulocytes (0.01 – 0.3%)
- Contain large cytoplasmic granules which obscure nucleus under microscope
- Cells store histamine in the granules. It increases the permeability of the capillaries to white blood cells, to allow them to engage pathogens in the infected tissues
- Often found in parasitic infections
What is the complement system?
- it bridges a gap between adaptive and innate immunity.
- The complement response does not change over time
Has 3 activation pathways
- Promote phagocytosis of microbes (opsonisation)
- Stimulate inflammation – activate Mast Cells and Neutrophils
- Also stimulate activation of B Cells and Ab production
Note: all lead to the lysis of the target cell.
What are cytokines?
Chemicals used by cells to communicate with other cells.
What are the functions of Lymphatic System?
- Drainage of tissue(lymph vessels)
- Absorption and transport of fatty acids and fats
- Immunity
Lymphatic Vessels
- Only carry fluid away from the tissues.
- Smallest are the lymphatic capillaries which begin in the tissue spaces as blind-ended sacs which are highly permeable
- Walls are composed of endothelium in which simple squamous cells overlap to form one-way valves
Primary Lymphoid Organs
Places where blood cells are made and mature (receive their ‘early training) :
- Bone Marrow
- Thymus
Secondary Lymphoid Organs
Sites of Lymphocyte activation (by antigens)
- Lymph node
- Spleen
- Toncil
Lymph node function
- Filter and purify the lymph before it reaches the venous system
- 99% of antigen will be removed in the lymph node
- In response to antigen detection (APC)T cells and B cells are stimulated and adaptive immune response is initiated
- Maintain and produce B cells and house T cells
Lymph node and lymphatic system pic
Lymphatic drainage pic
what is the function of T-cells?
T cells are responsible for cell mediated immunity(cytoxic or CD8+) and assisting B cells( Helper or CD4+ ).
T-cell selection:
- T cells must ‘learn’ not to recognise our own ‘self’ antigens.
- They must also be restricted to recognise Ag in association with our own MHC.
- The major histocompatibility complex is a set of cell surface proteins essential for the acquired immune system to recognize foreign molecules in vertebrates, which in turn determines histocompatibility
Purpose of MHC Class l
- Found on virtually all nucleated cells.
- Presents ‘virally induced’ peptides to CD8+ T cells and trigger cytotoxic response.
Purpose of MHC Class ll
- Found only on ‘Professional Antigen Presenting Cells’ (APCs).
- Presents exogenously produced Ag to CD4+ T cells (helpers)
- Activates macrophages and B cells
Difference between T cell and B cell lympocytes in recognition of Antigen?
- B cells – recognise free organic antigen via B Cell Receptors (BCR)
- T cells need to be shown protein antigen in association with MHC
What is the role of B cells in immunity?
- Mature into Plasma Cells
- Plasma cells are responsible for antibody (Ab) production.
- Express surface immunoglobulin (sIg) which is the antigen receptor for the B cell
what is self-tolerence?
The body’s immune defenses do not normally attack tissues that carry a self marker.
T Helper Cells (Th)
- Cannot kill infected cells or pathogens
- Activate and direct other immune cells
- Essential in B cell Ab class switching
- Essential in activation and growth of Tc
Cytotoxic T Cells
- When exposed to infected / dysfunctional somatic cells Tc Cells release perforin
- Forms pores in the target cell
- Also release Granzyme B, a protease, that can enter target cells via the perforin-formed pore and induce apoptosis
T Cell Memory
- Memory T cells can arise from fully differentiated T cells or from T cells which are only partially differentiated – allowing potential for further differentiation on re-exposure to the antigen.
B Cell (and T cell) Tolerance
- Both B Cells and T Cells can be made tolerant, but it is more important to tolerize T cells than B cells because B cells cannot make antibodies to most antigens without the help of T cells.
- B cells which recognise self Ag die in the bone marrow by apoptosis
Defintion: a state of unresponsiveness of the immune system to substances or tissue that have the capacity to elicit an immune response in given organism. It contrasts with conventional immune-mediated elimination of foreign antigens
Antibody Structure pic
5 different classes of Antibody
Immunoglobulins (Ig) are the proteins with antibody activity- 5 classes
- Primary response (IgM): Good at fixing compliment and opsonization (kill bacteria)
- Secondary response (IgG): Good opsonizer (crosses placenta)
- Mucosal immunity (IgA): Protects mucosal surfaces, resistant to stomach acid (Neutralisation)
- Allergy and helminth infection (worm-like parasites) (IgE): can causes anaphylactic shock
- IgD – No known Ab function
Opsonisation
Opsonisation is a term that refers to an immune process bacteria are targeted for destruction by phagocytes. The process of opsonization is a means of identifying the invading particle to the phagocyte.
