How the body responds to infection Flashcards
Where do lymphocytes develop from?
Pluripotent stem cells in the primary lymphoid organs
B lymphocytes- fully mature in bone marrow
T lymphocytes- Leave bone marrow in bloodstream to mature in the thymus
When lymphocytes are released from primary lymphoid organs what happens?
Circulate in body to secondary lymph tissue- here the lymphocytes accumulate
E.g. Lymph nodes found throughout body , spleen and mucosa- associated lymph tissues: lining of respiratory tract, GI, urinary tract, tonsils and adenoids
Explain lymphocyte recirculation
- Can cross walls into secondary lymphoid tissue e.g. spleen/ lymph node for 1/2 days then circulate around in the bloodstream
- Leave lymph nodes via efferent lymphatic at major point between blood circulation and lymphatic system- thoracic duct
- Some lymphocytes will enter peripheral tissues- drain out of tissues into tissue fliud and enter afferent lymphatics going back to the lymph node
- Majority lymphocytes come straight from blood into lymph node, yet some does still come from peripheral tissue
Different types of infectious organisms? Is bodies response to these the same/ different and what may be a consequence of 1 part of the immune response being impaired?
- Viruses
- Bacteria
- Fungi
- Protozoa
- Worms/ Helmets
- 1st 4 all simple unicellular but worms multicellular
- Effective immune system must defend against all these infectious agents
- Hence some individuals mat be able to deal with some infectious agents and not others
Outline briefly ways of classifying immune cells
- Leukocytes/ WBC- immune cells all produced from haematopoietic stem cells in the bone marrow
- Include neutrophils, basophils, eosinophils, monocytes and leukocytes
- Derived from myeloid (bone marrow) lymphoid tissue
- Myeloid and lymphoid lineages both are involved in dendritic cell formation. Myeloid cells include monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, and megakaryocytes to platelets. Lymphoid cells include T cells, B cells, and natural killer cells.
- Granulocytes- susceptible to dying revealing their granules- neutrophils, eosinophils, basophils
- Others Agranulocytes
- Polymorphonucleocytes- lobulated nuclei same as above but especially neutrophils due to lobed appearance
Define recognition and defence
Recognition- interaction with microbes and their components
Defence- elimination of microbes and their produces
Explain the innate immune response
Innate immune response- same quick response to infection hence moderate efficiency
- General recognition occurs of PAMPS (pathogen associated molecular patterns)
- Recognised by PRR- pattern recognition receptors
Explain features of adaptive immune response
- slowly activated
- High efficiency fully able to fight infection due to recognition of microbes down to sub-species level due to antigen receptors specific to the antigen
- Lymphocytes will have specific antigen receptors which are clonally expressed (all in same clone have same receptor)
Define an antigen
anything specifically recognised by a lymphocyte of the body (functionality defined)
Primary immune response
1) Skin contains epithelial barrier consisting of a hard keratinised surface- if this is cut microbe can get into the soft underlying dermal tissues (warm nutritious environment ideal for replication
2) Immediate (innate) local response- macrophages activated by binding to the PAMP of the bacteria, complement proteins interact with the surface of the microbe making holes in cell wall
3) Early induced response (innate/ inflammatory)- inflammatory mediators form activated macrophages and mast cells, complement proteins also act as mediator
- Activates walls of nearby blood vessels, making leaky- causing fluid to enter infected tissues causing inflammation
4) Later adaptive immune response- dendritic cells carry processed antigen to the lymph node or soluble antigens carried in lymph
- Activation of specific T and B cells occur which can bind to specific antigen (clonal secretion)
- Clonal expansion occurs
- Recirculate to site of infection
- Some lymphocytes form memory cells
Different categories of infections
- Extra-cellular pathogen- don’t penetrate cells- susceptible to anything that gains access to surface- complement proteins, phagocytes or antibodies
- Intracellular cytosolic pathogen- viruses (not free living parasites that need cells machinery to replicate)- interferons proteins interfere with virus replication, natural killer cells, cytotoxic T cells
- Intra-cellular vesicular pathogen- survive within the vesicles of the macrophage- have to by hyper-stimulated by helper T cells to help degrade ingested pathogen
What is immunopathology and outline different types
Diseases involving defects in, or inappropriate activity of, the immune system
- Immunodeficiency, allergy, autoimmunity, transplant rejection and lymphoproliferative diseases
Outline immunodeficiency
Immune system does not function properly- partial/ full impairment of the immune system so patient unable to effectively resolve infections and disease
- Primary immunodeficiencies- due to genetic defects
- Secondary immunodeficiencies- caused by environmental factors- HIV/AIDS/ malnutrition
Outline allergy
- Inappropriate triggering of the immune system caused by external stimuli e.g. allergens
- Pollen granules act as antigens which activate lymphocytes causing inflammation in airways and deeper in lungs in asthma
- Food allergies- leading to anaphylaxis
- Contact dermatitis e.g. nickel allergy
Outline autoimmunity
Autoimmunity= immune system triggered by auto-antigens activating auto-reactive lymphocytes causing autoimmune disease
e.g. in rheumatoid arthritis (attack on synovial joints- damage and degradation
