adaptive_immune_system_flashcards
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What are the components of the adaptive immune system?
Humoral immunity (B lymphocytes and antibody), Cellular immunity (T lymphocytes - CD4 T & CD8 T cells), Soluble components (Cytokines and chemokines).
What is ‘humoral’ immunity?
B lymphocytes and antibody.
What is ‘cellular’ immunity?
T lymphocytes - CD4 T & CD8 T cells.
What are the soluble components of the adaptive immune system?
Cytokines and chemokines.
What are the primary lymphoid organs involved in lymphocyte development?
Bone marrow and thymus.
What cells are derived from haematopoietic stem cells in the bone marrow?
Both T and B lymphocytes.
What is the site of B cell maturation?
Bone marrow.
Where do T cells mature?
Thymus.
When is the thymus most active?
In the foetal and neonatal period.
What happens to the thymus after puberty?
It involutes.
What are the secondary lymphoid organs?
Spleen, Lymph nodes, Mucosal associated lymphoid tissue.
What is the role of secondary lymphoid organs?
They are anatomical sites of interaction between naïve lymphocytes and microorganisms.
Where do T cells arise from and where do they mature?
They arise from haematopoietic stem cells and mature in the thymus.
What do all T cells express?
CD3+ and either CD4+ or CD8+.
What do CD8+ T cells recognize?
Peptides presented by HLA class I molecules.
What do CD4+ T cells recognize?
Peptides presented by HLA class II molecules.
What do CD4+ T cells (Helper lymphocytes) recognize?
Peptides derived from extracellular proteins presented on HLA Class II molecules (HLA-DR, HLA-DP, and HLA-DQ).
What are the immunoregulatory functions of CD4+ T cells?
Cell-cell interactions and expression of cytokines.
What are the different effector subtypes of CD4+ T cells and their functions?
Th1 (help CD8 and macrophages), Th2 (humoral response), Th17 (help neutrophil recruitment).
What cytokines do Th1 cells produce?
IL-2, IFN-ϒ, TNF.
What cytokines do Th2 cells produce?
IL-4, IL-5, IL-6.
What cytokines do Th17 cells produce?
Il-17, IL-21, IL-22.
What do CD8+ T cells (Specialised cytotoxic cells) recognize?
Peptides derived from intracellular proteins in association with HLA class I (HLA-A, HLA-B, HLA-C).
How do CD8+ T cells kill cells directly?
Perforin (pore forming) and granzymes & Expression of Fas ligand.
What cytokines do CD8+ T cells secrete?
IFNg, TNFa.
What is T cell memory?
Response to successive exposures to antigen is qualitatively and quantitatively different from that of first exposure.
How is the response of memory T cells different from naïve cells?
They are more easily activated than naïve cells.
How do B cells mature?
Stem cells in bone marrow become lymphoid progenitors pro B cells pre B cells IgM expressing B cells.
What happens to IgM expressing B cells upon antigen engagement?
They develop into plasma cells that secrete IgM or undergo germinal centre reaction to develop into plasma cells expressing IgG, IgE, and IgA.
What is central tolerance of B cells?
No recognition of self-antigens survive; Recognition of self-antigens in bone marrow negative selection to avoid autoreactivity.
How are B lymphocytes activated?
B cell receptor (surface expressed Ig) binds to antigen, some B cells mature to plasma cells secreting IgM.
What occurs during the germinal centre reaction?
Rapid B cell proliferation, isotype switching, and somatic hypermutation.
What do dendritic cells do in the activation of B cells?
Prime the CD4+ T cells.
How do CD4+ T cells help B cell differentiation?
Requires CD40L:CD40 interaction.
What complex genetic rearrangements do B cells undergo?
Isotype switching to IgG, IgA, or IgE; Somatic hypermutation to generate high affinity receptors.
What is isotype switching?
The process where a B cell changes the class of antibody it produces without altering the specificity for antigen.
What is somatic hypermutation?
A process that introduces mutations into the variable region of the antibody genes, enhancing antigen binding.
What further differentiation can B cells undergo?
Plasma cells producing IgG, IgA, or IgE antibody; long-lived memory cells.
What are immunoglobulins made of?
Two heavy chains and two light chains.
What determines the antibody class?
The heavy chain.
What are the subclasses of antibodies?
IgM, IgG, IgA, IgE, IgD; subclasses of IgG and IgA.
How is antigen recognized by antibodies?
By antigen binding regions (Fab) of both heavy & light chains.
What determines the effector function of antibodies?
The constant region of the heavy chain (Fc).
What are the functions of antibodies?
Identification of pathogens and toxins (Fab mediated); Interact with other components of immune response to remove pathogens (Fc mediated).
How do antibodies interact with other components of the immune response?
Complement, Phagocytes, Natural killer cells.
Why are antibodies particularly important?
In defense against bacteria of all kinds.
What is B cell memory?
Response to successive antigen exposure is qualitatively and quantitatively different from that of first exposure.
How is the response to successive antigen exposure different from the first exposure?
Lag time is decreased to 2-3 days, the titre of antibodies is greatly increased, response is dominated by IgG antibodies of high affinity, may be independent of CD4+ T lymphocytes.
What is the lag time between antigen exposure and antibody production in a memory response?
2-3 days.
How is the titre of antibodies different in a memory response?
Greatly increased.
What dominates the response in a memory B cell reaction?
IgG antibodies of high affinity.
Is the response of memory B cells dependent on CD4+ T lymphocytes?
It may be independent of help from CD4+ T lymphocytes.
