PMI02-2002 Flashcards
What is the immune system?
A vast communication network of cells and chemical signals distributed in blood and tissues throughout body
Regulates normal growth and development
Protects against disease
What causes smallpox?
Variolavirus
What caused the Black Death (plague)?
Yersinia pestis
What does the term “animalcules” refer to?
Bacteria (Antoine van Leeuwenhoek, Father of infection)
What was used to vaccinate against smallpox?
Cowpox - less virulent
Who invented the concept of handwashing?
Ignaz Semmelweis
Who discovered the first virus and name the virus?
Dmitri Ivanovsky
Tobacco Mosaic virus
Who discovered the flavivirus?
Walter Reed (causes yellow fever)
What cells are derived from the common lymphoid progenitor?
B cells
T cells
NK cells
What cells are derived from the common myeloid progenitor?
Megakaryocyte/erythrocyte precursor (platelets and erythocytes)
Granulocyte/macrophage precursor (granulocytes)
What are the two derivatives of the pluripotent haematopoietic stem cell?
Common lymphoid progenitor
Common myeloid progenitor
Where do immune cells originate from?
Bone marrow
What are the primary lymphoid organs?
Bone marrow
Thymus
What are the main secondary lymphoid organs?
Tonsils and adenoids
Spleen
Lymph nodes
Peyer’s patches
What is immunity?
Condition/process that permits innate and adaptive resistance to disease
What are the requirements for an effective immune system?
Recognise a wide range of infectious micro-organisms
Defend against both intra- and extracellular pathogens
Tolerate commensals
Prevent/limit damage to self
Respond quickly
What are the main differences between innate and adaptive immunity?
Innate = immediate and non-specific
Adaptive = delayed and specific
What three main types of physical barriers are present with epithelium?
Mechanical
Chemical
Microbiological
What mechanical barriers are in place for epithelia?
Tight junctions
Longitudinal flow of air/fluid (skin, gut)
Mucus, cilia (lungs)
How does smoking affect the epithelial barrier?
Burns and kills cilia, decreasing the mechanical barrier
What chemical barriers are in place for epithelia?
Fatty acids (skin)
Low pH and enzymes (stomach)
Salivary enzymes (mouth)
Antimicrobial peptides
What microbiological barrier is in place for epithelia?
Normal, commensal flora
Give examples of antimicrobial peptides.
Defensins
Histatins
Cathelicidin (LL37)
What do histatins target?
Fungi
What are the two types of defensins and where are they found?
α = produced by neutrophils
β = fluids
What cells produce cathelicidin?
Neutrophils
Epithelial cells
What are the three ways in which the complement system can be activated?
Classical pathway
Mannose-binding lectin pathway
Alternative pathway
What are the three main functions of the complement system?
Inflammation
Opsonisation
Killing of pathogen
What is the main complement molecule responsible for opsonisation?
C3b
What complement molecules are responsible for inflammation?
Anaphylatoxins
What complement molecules are responsible for killing pathogens?
MAC/membrane attack complex = C5-9
What is the complement system?
System of serum proteins that are sequentially activated to attach to pathogen surfaces, recruit inflammatory cells and kill pathogens
Describe the process of phagocytosis.
- Recruited by chemokines (eg CXCL8) or complement
- Bind microbe - recognition aided by C3b or antibodies; pattern recognition receptors may be used
- Internalise microbe into a phagosome
- Fusion with lysosome to create a phagolysosome
- Microbe killed (oxygen radicals and enzymes)
What is involved in innate immunity?
Physical barriers
Natural humoral components
Recruitment and activation of phagocytes
Activation of adaptive immunity
What cell bridges innate and adaptive immunity?
Dendritic cells
What is the main function of dendritic cells?
Capture microbes and transport to lymph nodes to induce adaptive immunity
Describe what occurs when a dendritic cell encounters a microbe in the skin.
- Langerhans cell recognises pathogen with pattern recognition receptor and sample it/take it up
- Langerhans cell leaves epithelium and enters lymphatic system whilst processing antigen
- Mature dendritic cell enters lymph node and transfers some antigen to resident dendritic cells
- B7-positive dendritic cells stimulate naive T cells (Th0)
- T cells activate B cells
- T and B cells leave to infected tissue
What type of antigens are presented on MHC class I molecules?
Internal pathogens (viral)
What type of antigens are presented on MHC class II molecules?
External pathogens
Which T cells recognise MHC class I complexes?
CD8+/cytotoxic
Which T cells recognise MHC class II complexes?
CD4+/helper
What does MHC stand for?
Major histocompatibility complex
What kind of animals possess adaptive immunity?
Vertebrates
What is found in the paracortical areas of a lymph node?
T cells mainly
What is found in the germinal centers of a lymph node?
B cells mainly
Describe what occurs when a mature dendritic cell enters a lymph node.
Enters via afferent lymphatic vessel to the paracortical area to interact with T cells
Activated Th2 cells move to germinal center to activate B cells
T and B cells leave via efferent lymphatic vessel
What are the co-stimulatory molecules for T cell receptors?
CD8 or CD4
What is CD3 and what does it recognise?
T cell receptor
Recognises specific MHC-antigen complexes
Describe the function of a cytotoxic T cell
Primed in lymph node and patrols body
When it encounters a cell expressing its specific viral antigen, it attaches and kills the cell
Via granzyme and perforin
What is the function of Th1 cells?
(Cellular immunity) recruitment of Tc cells and macrophages to eliminate pathogen
What is the function of Th2 cells?
(Humoral immunity) binds B cells in germinal center to cause antibody production
What is the function of Th17 cells?
(Cellular immunity) recruitment of neutrophils for bacteria and fungi elimination
What is the function of Treg cells?
Suppress of modulate the immune response and protects against autoimmunity
Describe the basic structure of an antibody.
Y-shaped protein
Fc and Fab fragments/regions
What is the function of memory cells?
Patrol body and produce a rapid response when they encounter the same pathogen (differentiate into plasma cells)
What happens when normal signals for growth and cell death fail?
Cancer/tumour
