Development of Immune Cells Flashcards
What is the principal function of lymphocytes?
- Specific recognition of antigens
- B lymphocytes: mediators of humoral immunity
- T lymphocytes: mediators of cell-mediated immunity
Name 4 antigen-presenting cells
- Dendritic cells
- Macrophages
- B cells
- Follicular dendritic cells
What are the principal function(s) of antigen-presenting cells?
- Capture of antigens for display to lymphocytes
- Dendritic cells: initiation of T cell responses
- Macrophages: effector phase of cell-mediated immunity
- Follicular dendritic cells: display of antigens to B cells in humoral immune response
Name 3 effector cells and their role
- T lymphocytes: activation of phagocytes, killing infected cells
- Macrophages: phagocytosis + killing of microbes
- Granulocytes: killing microbes
All result in elimination of antigens
Where are immune cells generated?
Bone marrow
What are the two specific lineages of immune cells?
- Myeloid
- Lymphoid
Which lineage are the following derived from?
- neutrophils
- macrophages
- dendritic cells
- mast cells
- eosinophils
- basophils
- natural killer cells
- B cells
- T cells
All generated in the bone marrow, all are from myeloid lineage EXCEPT natural killer cells, B cells & T cells which come from the lymphoid lineage.
Dendritic cells are a type of antigen-presenting cell, they present the antigen bound to MHC. Where exactly do dendritic cells go to induce T lymphocyte activation?
- Dendritic cells express membrane bound molecules + chemokine receptors
- Chemokine receptors allow dendritic cells to migrate to lymph nodes
- Here, there are naive T cells + B cells
- Dendritic cell can present its antigens to the T cells here
- Activation doesn’t happen in skin/gut/airways but happens in lymph nodes
What is the role of natural killer (NK) cells?
- kill virus-infected cells
- kill malignantly transformed cells (cancer cells)
- express cytotoxic enzymes (lyse target cells)
Both subsets of lymphocytes have similar morphology but different functions. How so?
- T cells - for cellular immunity
- B cells - for humoral immunity, prod antibodies
Describe Th (helper) cells
- Express CD4+
- Activate macrophages
- Help B cells to produce antibodies
- Th1, Th2, Th17 cells
Describe CTL (cytotoxic) T Cells
- Express CD8
- Kill cells infected with microbes
- Kill tumour cells
Describe Treg (regulatoy) cells
- inhibit function of other T cells + immune cells
- control of immune responses
What are the 3 subsets of B lymphocytes?
- Follicular B cells (majority)
- Marginal Zone B cells
- B-1 cells
All produce different types of antibodies
Most immune cells are released into blood and are ready to work, such as granulocytes and monocytes. What about your resident APCs?
- APCs - Dendritic cells & macrophages
- These are present in all organs/tissues + especially at portals of entry (skin, airways, gut)
Where does lymphocyte maturation occur?
- Immature T cells enter thymus where they continue maturation until stage of mature naïve T cells
- Immature B cells continue maturation in bone marrow until stage of mature naïve B cells
What are the central lymphoid organs and what are the peripheral lymphoid organs?
- Central = bone marrow, thumus
- Peripheral = lymph nodes, spleen, mucosal + cutaneous lymphoid tissue
The mature lymphocytes can travel from the central to peripheral lymphoid organs via blood + lymph.
Immature lymphocytes are tested for the ability of what 2 things?
- to recognise foreign antigens (ags) - useful
- respond to self antigens - not useful + dangerous
What is meant by the “checkpoints” in lymphocyte maturation?
- Start with pro-B/T cell
- Undergo proliferation
- Pre-B/T cell expresses one chain of antigen receptor
- Failure to express pre-antigen receptor -> cell death
- Otherwise again proliferate
- Some die
- Surviving immature B/T cell expresses complete antigen receptor
- weak antigen recognition -> positive selection -> MATURE B/T cell
- strong antigen recognition -> negative selection (suggest self-antigen, dangerous)
What are the stages of T cell maturation + selection?
What are the 3 main outcomes of lymphocyte maturation?
What is meant by “self / non-self discrimination”?
The immune cells are responsible for eliminating and controlling microbes and not to damage the host.
They should be able to discriminate between the host’s self antigens and the microbes’ foreign (non-self) antigens.
In what manner are antigen receptors of T/B cells generated? What is a consequence of this?
Random generation occurs so…
- self-reactive lymphocytes generated
- self-antigens have access to immune cells
High likelihood of generating lymphocytes that have the potential to react against self-antigens (self-reactive lymphocytes)
What is self tolerance?
- AKA immunlogical tolerance
- When self-reactive B/T cell have immunlogical unresponsiveness to self antigens -> self tolerance
