Lymphocytes Flashcards
What is adaptive immunity?
An adaptive immune response is initiated when a pathogen overwhelms innate defence mechanisms.
As the pathogen replicates and antigen accumulates, sensor cells of the innate immune system become activated to trigger the adaptive immune response.
Expansion of antigen-specific lymphocytes that target the pathogen specifically and to the formation of memory cells that provide long-lasting specific immunity.
What major event triggers the adaptive immune system activation?
B or T lymphocytes encounter antigens (corresponding to a pathogen) for which their receptors have specific reactivity]
3 hallmarks of adaptive immune response?
Creates immunological memory => more rapid and heightened immune response upon re-exposure to same pathogen
Highly specific; With the ability to recognise “non-self” antigens in the presence of “self”, during the process ofantigen presentation (possible through the highly variable antigen receptors)
Long-lasting protection
What is the problem with specificity of antibodies?
We are exposed to a large amount of different microbes and hence antigens – no predicting which ones.
The adaptive immune system is highly specific but needs to respond to them all.
To do so there must be a very large pool of cells with specific receptors (large repertoire of lymphocytes receptors) that can recognise these huge array of antigens.
How is diversity generated in the adaptive immune response?
Immunoglobulin gene rearrangement -
Each BCR receptor chain (kappa, lambda and heavy chain genes) is encoded by separate multigene families/clusters on different chromosomes
During B cell maturation (in bone marrow) these gene segments are rearranged and brought together
Note that the T-cell receptor gene segments are arranged in a similar pattern to immunoglobulin gene segments and are rearranged by the same enzymes (occurs in the thymus).
Can you think of any problems with this process of gene rearrangement?
With so many different antigen receptors being generated randomly during the lifetime of an individual, there is a possibility that some receptors might react against an individual’s own self antigens.
Which cells are lymphocytes and what process are they produced by?
Lymphopoiesis -
B cells
T cells
Natural killer cells
What are the two primary cells of the immune response and which response are they part of?
T-cells - cell mediated response
B-cells _ humoral/antibody response
What are the differences between T-cells and B-cells?
T-cells mature in thymus and B cells in bone marrow
T-cells inside lymph nodes- peyers patches, B cells are outside
B cells have immunoglobulin receptors, T cells have CD receptors
What are the three types of T cells and what are their functions?
Natural killer/cytotoxic - kills cells infected with viruses or other intracellular pathogens bearing the antigen
Helper T cells - Provide signals often in the form of specific cytokines which activate the function of other cells such as B-cell production/macrophage killing
Regulatory T cells - supress activity of other lymphocytes and help limit possible damage
Which molecule distinguishes T helper and T killer cells?
CD4 – helper
CD8 - killer
What do Th1 cells do?
B cell class switching, macrophages and inflammation
produce cytokines IFN-γ (+ Tumour Necrosis Factor + Interleukin 12)
Extra explanation: Promote B cell class switching that favours production of IgG antibodies Help to eradicate infections by microbes that can survive or replicate within macrophages (evade the intracellular killing mechanisms/fusing with lysosomes recognises antigens on infected macrophages activates the macrophage further through the release of IFN-γ, enabling them to destroy intracellular microorganisms more efficiently
What do T-helper cells produce?
Cytokines
What do Th2 cells do?
allergies and worm
production of IL-4, IL-5, and IL-13.
extra:
control infections by extracellular parasites, particularly helminths, by promoting responses mediated by eosinophils, mast cells, and IgE
required for class switching of B cells to produce IgE, the primary role of which is to fight parasitic infections.
IgE is also the antibody responsible for allergies – so pro-allergic
What does Th17 do?
neutrophils, bacteria and fungi
TH17 cells produce the cytokines IL-17, IL23, IL-6
Induced in response to extracellular bacteria and fungi, and amplify neutrophilic responses that help to clear such pathogens
What do Tfh cells do?
B cell support
Produce IL-21
T follicular helper (TFH) cells interact with B cells to regulate antibody production during the immune response
What do Tr regs do?
NO IMMUNE RESPONSE
Produce IL-10, TGF-ß
T regs are anti-inflammatory
Limit the immune response/supress T cell responses
What are the 5 types of CD4 T-cells?
Th1 - B cell class switching, macrophages and inflammation
Th2- Parasitic/allergic
Th17 - bacteria, virus and fungi
Tfh - B cell support
Tregs - no immune response
How do T helper cells contribute to B cell activation?
Effector T cells express surface molecules and cytokines that help the B cell to proliferate and to differentiate into antibody-secreting cells (plasma cells) and into memory B cells
Fine tuning of antibody responses to increase the affinity of the antibody for the antigen and the switching to most immunoglobulin classes other than IgM depend on the interaction of antigen-stimulated B cells with helper T cells.
How do T helper cells contribute to B cell activation?
Effector T cells express surface molecules and cytokines that help the B cell to proliferate and to differentiate into antibody-secreting cells (plasma cells) and into memory B cells
Fine tuning of antibody responses to increase the affinity of the antibody for the antigen and the switching to most immunoglobulin classes other than IgM depend on the interaction of antigen-stimulated B cells with helper T cells.
