Overview Flashcards
What are the two circulatory systems in the body?
The blood and the lymphatic system
What is the lymphatic system comprised of?
The primary and secondary lymphoid organs
Primary lymphoid organs: B and T cells
Secondary lymphoid organs: These organs include the lymph nodes, the spleen, the tonsils and certain tissue in various mucous membrane layers in the body (for instance in the bowel)
What is the origin of all immune cells?
The bone marrow
What occurs in the secondary lymphoid organs?
Naïve mature B, T cells interact with antigens via antigen presenting cells (APC)
A naïve B cell is a B cell that has not been exposed to an antigen
How do B cells differentiate and what do they form?
The antigen-dependent phase of B cell development occurs following B cell activation by antigen binding and co-stimulation. These signals promote B cell differentiation into either memory B cells or terminal, antibody-secreting plasma cells.
How do T cells differentiate and what do they form?
They recognise foreign particles (antigen) by a surface expressed, highly variable, T cell receptor (TCR). There are two major types of T cells: the helper T cell and the cytotoxic T cell
Primary and secondary lymphoid organs
The purple structure in the diagram shows a lymph node structure
Tell me the cellular ‘players’ in the immune system
Tell me the branches of the immune system, what the starting cell is and what this forms.
Also tell me whether they are part of the innate or adaptive immune system
- Platelets and erythrocytes not really part of innate response just immune system so won’t be talked about much
- Dendritic cells bridge the gap between the innate and adaptive immune system
- NK cells are innate but is also sometimes considered part of adaptive immunity
- Some dendritic cells have been found to have come from lymphoid progenitors not just myeloid progenitors
Tell me about the cluster of differentiation (CD) antigens?
What CD do all immune cells present?
The CD antigens are markers expressed by all types of cells, they are expressed in different concentrations but they help identify each type of cell.
All immune cells express CD45
NOTE: Some have a little bit more or a little bit less CD (not a matter of have it or don’t have it)- hence why may be some confusion
Label the CD antigens of the following immune cells…
Tell me the about the CD14 antigen
Co-receptor with TLR4 for detection of bacterial lipopolysaccharide (LPS) in presence of LPS binding protein (LPB)
Tell me about the MW of cytokines an chemokines
What does this help with?
- Low MW proteins – cell-cell communication
- Easily soluble and mobile around immune system
What do cytokines and chemokines bind to and regulate?
Specific receptors- signal transduction and modulate gene expression in target cell
Tell me about the affinity of cytokines and chemokines, what does this mean about the concentrations of both needed in the immune resposnse?
Very high affinity 1010-1012M (very specific and potent)– work at low concentrations
Tell me about the proximities that cytokines and chemokines work at?
What type of messengers are they?
They work at very different levels, either Autocrine/paracrine (close)/endocrine (distal parts of body via circulation and are generally intercellular messengers
What else do cytokines and chemokines regulate?
Regulate kinetics, intensity of immune response
What are cytokines secreted by?
Cytokines secreted by leukocytes: Interleukins e.g., IL-2 and Chemokines that affect chemotaxis and trafficking and other cells (endothelial/stromal cells/fibroblasts)
What is IL-2 a growth factor for?
T-cells
What do chemokines help to do?
Direct immune cells where to go so they are fighting infection in the correct location of the body
What is an antigen and what are some names that it is often referred to as?
Substance that induces a specific immune response is usually called an antigen or immunogen e.g., Spike protein from Covid
What is meant by Antigenicity?
Ability for antigen to be specifically recognised by the immune response e.g., antibodies or T cell receptor
What is meant by immunogenicity?
Ability of an antigen to induce an immune response (humoral or cellular)- don’t always want high immunogenicity as you want it to be controlled
Basic overview of the immune system
https://www.youtube.com/watch?v=la6nXuAw-Oo
Tell me the timeline for the course of normal immune response action and the types of immune response and cells active in each part?
- 3-4 weeks needed for a good antibody response
- 1-2 weeks for T and B cells (if never had the infection before)
- The timeline above is shifted to the left if had the infection before
