24 Questions
What is the primary function of immunological tolerance in the immune system?
To distinguish between self and non-self, preventing harmful immune responses.
What happens when tolerance mechanisms fail?
It can lead to the development of autoimmune diseases.
What is the purpose of immune regulation and tolerance in the immune system?
To prevent inappropriate reactions against self-antigens and harmless environmental antigens, and to avoid excessive lymphocyte activation and tissue damage.
What is the primary mechanism by which peripheral tolerance is induced?
mature T cells recognizing self antigens in peripheral tissues
What is the significance of central tolerance in preventing autoimmune diseases?
It prevents the development of autoimmune diseases by eliminating or inactivating autoreactive T cells.
What is anergy in the context of immunology?
functional inactivation of T lymphocytes due to lack of co-stimulatory signals
What are the two signals required for the proliferation and differentiation of naive T lymphocytes?
antigen (signal 1) and co-stimulators (signal 2)
What is the therapeutic potential of inducing tolerance?
It may be exploited to prevent graft rejection, treat autoimmune and allergic diseases, and prevent immune responses in gene therapy and stem cell transplantation.
What is the consequence of the breakdown of tolerance?
It leads to the development of autoimmune diseases.
What is the role of inhibitory receptors in the immune system?
to maintain a balance between activation and inhibition
Where do regulatory T cells develop, and what is their function?
thymus or peripheral tissues; block activation of harmful lymphocytes specific for self antigens
What is the role of genetic and environmental factors in the loss of tolerance?
They contribute to the loss of tolerance and the initiation of autoimmunity.
What is the significance of molecular mimicry in autoimmune pathogenesis?
It is a mechanism by which the immune system mistakenly attacks the body's own tissues, leading to autoimmune diseases.
What is the cytokine required for the survival and function of regulatory T cells?
IL-2
What is the outcome when mature T cells recognize self antigens in peripheral tissues?
functional inactivation (anergy) or deletion (death)
What is the purpose of peripheral tolerance in the immune system?
to prevent autoimmunity when central tolerance is incomplete
Where does central tolerance occur during lymphocyte development?
Central tolerance occurs during lymphocyte development in the primary lymphoid organs (thymus and bone marrow).
What is the purpose of central tolerance?
The purpose of central tolerance is to eliminate or inactivate self-reactive lymphocytes through negative selection or clonal deletion.
What happens to self-reactive T cells in the thymus?
Self-reactive T cells are eliminated in the thymus.
What is the consequence of failure of central tolerance?
Failure of central tolerance can lead to the escape of autoreactive lymphocytes.
Where are self-reactive B cells eliminated?
Self-reactive B cells are eliminated in the bone marrow.
What is the mechanism by which self-reactive lymphocytes are eliminated in central tolerance?
The mechanism by which self-reactive lymphocytes are eliminated in central tolerance is through negative selection or clonal deletion.
Where do self-reactive lymphocytes originate from?
Self-reactive lymphocytes originate from the primary lymphoid organs (thymus and bone marrow).
What is the significance of central tolerance in the immune system?
Central tolerance is crucial for preventing autoimmune responses by eliminating self-reactive lymphocytes.
Study Notes
Central Tolerance
- Occurs during lymphocyte development in primary lymphoid organs (thymus and bone marrow)
- Involves elimination or inactivation of self-reactive lymphocytes through negative selection or clonal deletion
- Self-reactive T cells are eliminated in the thymus, while self-reactive B cells are eliminated in the bone marrow
- Failure of central tolerance can lead to the escape of autoreactive lymphocytes
Peripheral Tolerance
- Mechanisms operate outside primary lymphoid organs and act on mature lymphocytes
- Mechanisms include anergy, deletion, regulatory T cells (Tregs), and suppression by regulatory B cells
- Anergy refers to the state of functional inactivation of self-reactive lymphocytes
- Tregs are a specialized subset of T cells that suppress the activity of other immune cells, including autoreactive T cells
- Regulatory B cells secrete immunosuppressive molecules and regulate immune responses
Anergy
- Functional inactivation of T lymphocytes that occurs when they recognize antigens without adequate co-stimulators
- Naive T lymphocytes need two signals for proliferation and differentiation: Signal 1 is antigen, and Signal 2 is provided by co-stimulators
Regulatory T Cells
- Develop in the thymus or peripheral tissues on recognition of self antigens and block the activation of potentially harmful lymphocytes
- Most regulatory T cells are CD4+ and express high levels of CD25
- Survival and function of regulatory T cells are dependent on the cytokine IL-2
Inhibitory Receptors
- Present in NK cells, T cells, and B cells
- Used to maintain a balance between activation and inhibition
Learning Outcomes
- Define immunological tolerance
- Describe mechanisms of central and peripheral tolerance and their roles in preventing autoimmune diseases
- Identify consequences of breakdown of tolerance leading to autoimmune diseases
- Recognize genetic and environmental factors contributing to loss of tolerance and initiation of autoimmunity
Immune Tolerance
- Fundamental concept in immunology that ensures distinction between self and non-self
- Importance: prevents inappropriate reactions against self-antigens and immune responses against harmless environmental antigens
- Therapeutic potential: inducing tolerance can be exploited to prevent graft rejection, treat autoimmune and allergic diseases, and prevent immune responses in gene therapy and stem cell transplantation
This quiz covers the concept of central tolerance in immunology, including its occurrence in primary lymphoid organs such as thymus and bone marrow. It also explores the development of T cells and B cells.
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