Lecture 6 - The Immune System Flashcards
(43 cards)
What is the structure and function of the Lymphatic system?
- Lymphatic tissue/ organs and cells
- Bone Marrow
- Lymph - fluid similar to plasma
- Lymphatic vessels - carry lymph from periphery to venous system
Protects us against disease
Lymphoid cells respond to environmental pathogens, toxins and abnormal body cells
It produces lymphocytes
Returns fluid to blood
Distributes hormones to circulation
What are the pathogens that cause disease?
Viruses e.g. Epstein Barr
Fungi e.g. Candidiasis
Bacteria e.g. E.coli
Parasites e.g. Schistosome
Outline the production and distribution of lymphocytes
Production occurs in the lymphoid tissues, lymphoid organs and the red bone marrow
Distribution - travels through the lymphatic vessels and capillaries detects a problem and travels to the site of infection
What are lymphatic vessels and capillaries?
Vessels begin as capillaries which are closed on one end and are located between cells of many tissues
Capillaries merge to form lymphatic vessels which have thin walls and lots of valves to prevent backflow
What is the difference between a lymphatic vessels and blood capillaries?
Start as blind pockets rather than tubes
Have a larger diameter
Have thinner walls
Flat or irregular in section
Outline the lymph trunks and ducts
From the lymphatic vessels, lymph passes through the lymph nodes and then into lymph trunks
These include the lumbar, intestinal, bronchomediastinal, subclavian and jugular trunks
Lymph trunks then merge to form either the thoracic duct or the right lymphatic duct
What are the circulating lymphocytes?
T cells - thymus dependent
B cells - bone marrow derived
NK cells - Natural Killer cells - also bone marrow derived
How are lymphocytes produced and distributed?
In the red bone marrow, hemocytoblasts divide to form lymphoid stem cells these can either convert to B cells and NK cells or migrate to the thymus to produce T cells which are then transported to the circulatory system
What are the primary lymphatic organs?
Where immune cells become immunocompetent
Red bone marrow and the thymus
What are the secondary lymphatic organs?
Lymph nodes
Spleen
Lymphoid nodules
Outline the structure of the lymph node
Afferent lymphatic vessels enter then lymph moves through the subcapsular space which contains macrophages to the outer cortex - B cells within germinal centers
Deep cortex - T cells
Core - B cells and plasma cells - medullary cords organise these
Into the hilum and efferent lymphatics
What is the difference between lymph organs and lymphoid nodules?
Lymph organs are separated from surrounding tissues by a fibrous capsule
Whereas lymphoid nodules are a bundle of lymphoid tissue without the fibrous capsule
Outline the flow of lymph
Interstitial fluid
Lymph capillaries
Lymph vessels
Lymph trunks
Lymph ducts
Subclavian veins
What is the function of the lymph node?
A filter which purifies lymph before return to venous circulation
Removes debris, pathogens, 99% of antigens
Outline the distribution of lymph nodes
Gut, trachea, lungs and thoracic duct protect against pathogens in digestive and respiratory systems
Glands - Large lymph nodes at the groin and base of neck - swell in response to inflammation
Lymphadenopathy - Chronic or excessive enlargement of lymph nodes may be due to cancer
What is the difference between non specific immunity and specific immunity?
Non specific (innate) - Block or attack any potential pathogen, present from birth, no memory
Specific (adaptive) - identify, attack and develop immunity to a specific antigen, acquired in response to antigens
What are the 7 methods of non specific defense?
Physical barriers
Phagocytic cells
Immunological surveillance (NK cells)
Interferons (antiviral)
Complement system
Inflammation
Fever
Outline the method of physical barriers?
Eyes - washing with tears, lysozymes
Skin - Anatomic barrier sweat and sebum, antimicrobial secretion, low pH, commensal microbes
Respiratory tract - mucus, cilia, antibody, phagocytosis
Digestive tract - Stomach acidity, normal flora, intestine - alkaline pH, mechanical flushing, enzymes, bacteriocins
Genitourinary tract - washing by urine, vaginal lactic acid
Outline the method of phagocytosis and antigen presentation
Pathogen phagocytised by antigen presenting cell
Lysosome action produces antigenic fragments
ER produces Class 2 MHC proteins which are bound to antigenic fragments these are they displayed on the cell membrane
What are the classes of phagocytes?
Microphages - Neutrophils and eosinphils, leave the bloodstream, enter peripheral tissues to fight infections
Macrophages - Large phagocytic cells derived from monocytes, distributed throughout the body, make up monocyte-macrophage system, may be free or fixed
What are activated macrophages?
Respond to pathogens in several ways
Engulf pathogen and destroy it with lysosomal enzymes
Bind to pathogen so other cells can destroy it
Destroy pathogen by releasing toxic chemicals into interstitial fluid
Outline the method of immunological surveillance by NK cells
Recognition and adhesion of NK cell to abnormal cell
Realignment of golgi apparatus
Secretion of perforin
Lysis of abnormal cell
What are interferons?
Non specific response to viral infections
Proteins (cytokines) - released by activated lymphocytes and macrophages
Slow the spread of disease
What are the 3 types of interferons?
Alpha interferons- Produced by leukocytes, stimulate NK cells
Beta interferons - Secreted by fibrocytes, slow inflammation
Gamma interferons - Secreted by T cells and NK cells, stimulate macrophage activity
