Immunology Flashcards
Part of ICS
Haematopoiesis starting from haematocytoblast
splits to common myeloid progenitor and common lymphoid progenitor
Common myeloid progenitor—-> megakaryocyte, erythrocyte, mast cell, myeloblast
Myeloblast —->eosinophil, basophil, neutrophil, monocyte (—> macrophage)
Common lymphoid progenitor—> natural killer cell, lymphocyte (—> T cell, B cell—> plasma cell)
What are the primary lymphoid organs (where B cells and T cells come from)?
Both originate in bone marrow. B cells stay and mature in bone marrow but T cells move to the Thymus
What is thymic tolerance?
Thymus ensures that T cells produced are good at recognising foreign antigens and the suppressing the attack on self antigens. Some T cells produced can want to attack self antigens but they are destroyed by thymus. Dysfunction of the thymus leads to autoimmune diseases such as Myasthenia Gravis.
What are secondary lymphoid organs (where does the actual immune fighting happen?
It is in these organs where the cells of the immune system do their actual job of fighting off germs and foreign substances.
-Lymph nodes - Site of Dendritic Cells (It is in these organs where the cells of the immune system do their actual job of fighting off germs and foreign substances) , B and T cell interactions
- Spleen - RBC recycling, encapsulated bacterial cell killing
-tonsils
What are the tertiary lymphoid structures?
Tertiary lymphoid structures (TLSs) are organized aggregates of immune cells that form postnatally in nonlymphoid tissues. TLSs are not found under physiological conditions but arise in the context or in response to chronic inflammation, such as in autoimmune disease, chronic infection, and cancer.
Pathological
- Germinal centres of rapidly proliferating lymphocytes
Lymphocyte proliferation is defined as the process whereby lymphocytes begin to synthesize DNA after cross-linking of their antigen receptor either following recognition of antigen or stimulation by a polyclonal activator
Qualities of innate immunity?
Non-specific
- Rapid
- Already active (little activation needed)
- No memory
- Short duration
- Killing usually via complement activation
- Mediated by neutrophils and macrophages
Complement activation?
At the basic level the broad functions of the complement system can be split into three areas: (1) the activation of inflammation; (2) the opsonization (labeling) of pathogens and cells for clearance/destruction; (3) the direct killing of target cells/microbes by lysis.
Qualities of adaptive immunity?
- Specific
- Slow
- Needs activation
- Have memory
- Killing usually antibody mediated
- Main cells are T, B and plasma cells
- Long lasting
Examples of physical barriers
- Skin
Contains Chemical barriers (lysozymes in sebum and skin target microbes) - Mucus and cilia
Thick mucus secretions prevent pathogen entry
Antimicrobial substances (Protease + IgA ab)
mucociliary clearance in resp. tracts (waft away) mucosa lines Resp, GI and GU tracts
- Also contains MALT (Mucosa-associated lymphoid tissue)
(secondary lymphoid with lots of lymphocytes)
Examples of chemical barriers
- Lysozyme in tears
- Stomach acid
complement pathways?
- Classical
- Lectin
- Alternate
Complement system destroys foreign bodies by…
- Direct lysis - Membrane attack complex formation
- Opsonisation - Increased phagocytosis via protein C3b
- Inflammation - Macrophage chemotaxis via proteins C3a and C5a
One of the innate cells- neutrophils?
- Key mediator of acute inflammation - IL8 chemokine
- 70% of all leukocytes
- Act in hours-days
- Express CD66 receptor (common for all granulocytes-neutrophils, eosinophils, and basophils)
Innate cells - macrophages?
- Act over months-years (typically chronic)
- Phagocytosis, antigen presenting and cytokine secreting (TNF-a, IL1 and IL12)
- Express CD14+ and CD40+
- Can be circulating or resident (eg: Kuppfer cells, alveolar macrophages)
- Clear apoptotic debris
Innate cells: eosinophils
- Release major basic protein
- Seen in parasitic infections
Innate cells: basophils?
- Circulate mast cells
- Secrete serotonin and heparin and histamine
- Important in asthma, anaphylaxis, atopic dermatitis and hay fever
Innate cells: mast cells
- Important in parastic infections and allergic reactions
- Activate type 1 hypersensitivity: IgE crosslinking -> degranulation -> histamine release
- Fixed at tissues at mucosal surfaces
Innate cells: natural killer cells
- In blood and tissues
- Express CD16+
- Antibody-dependent cellular cytotoxicity
- Recognise self and non-self by the presence of MHC-I on cell surfaces
- Activation -> degranulation -> perforin -> perforates viral infected cells
Non-cellular components of innate immunity
Physical and chemical barriers
Receptors on innate cells
- Toll like receptors (TLRs) and nod like receptors that are pattern recognition receptors for pamps and damps
- Respond to PAMPs and DAMPs (One major category of inflammatory stimulation, is the family of pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). These patterns are found on bacterial cell walls, DNA etc.
Which toll like receptors are intracellular?
3, 7, 8, 9
(rest are extracellular out of 10)
What are antigen presenting cells?
- The interface between innate and adaptive immunity
- All present exogenous antigens in the presence of MHCII (major histocompatibility complex)
- Best cells for this are dendritic cells
- (macrophages and B-cells also do this)
Dendritic cell function?
- Present foreign antigens to T helper cells
- Stimulates further T helper proliferation
- Stimulates B cell production -> antibodies
What is formed when a dendritic cell and T helper cell communicate?
Immune synapse
3 conditions that must be met for antigen presenting cells to function
Receptor binding
- Co-stimulation (other molecules bind after primary receptor binding)
- Cytokine release
