Define immunocompetence and self-tolerance. How is self-tolerance achieved?

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1. Immunocompetence refers to the ability of the immune system to recognize and respond to antigens effectively. It involves the maturation and differentiation of immune cells, such as B cells and T cells, to perform their specific functions in identifying and neutralizing pathogens.
2. Self-tolerance is the immune system's ability to recognize the body's own cells and tissues as 'self' and not mount an immune response against them. This prevents autoimmune diseases, where the immune system mistakenly attacks the body's own cells.
3. Self-tolerance is achieved through several mechanisms during the development of immune cells. One key process is central tolerance, which occurs in the primary lymphoid organs (thymus for T cells and bone marrow for B cells). Here, developing lymphocytes that strongly react to self-antigens are eliminated through apoptosis, a process known as negative selection.
4. Another mechanism is peripheral tolerance, which occurs after lymphocytes have matured and entered the peripheral tissues. This involves regulatory T cells (Tregs) that suppress immune responses against self-antigens and mechanisms like anergy, where self-reactive lymphocytes become functionally inactive.
5. Together, these processes ensure that the immune system can distinguish between self and non-self, maintaining a balance that prevents autoimmunity while allowing effective responses to foreign antigens.

Key Concepts

Immunocompetence

Immunocompetence refers to the ability of the immune system to recognize and respond effectively to pathogens, such as bacteria and viruses. It involves the development and activation of immune cells, including T cells and B cells, which work together to identify and eliminate foreign invaders. A competent immune system is crucial for maintaining health and preventing infections.

Self-Tolerance

Self-tolerance is the immune system's ability to distinguish between the body's own cells and foreign cells. This mechanism prevents the immune system from attacking the body's own tissues, which could lead to autoimmune diseases. Self-tolerance is essential for maintaining homeostasis and preventing harmful immune responses against self-antigens.

Mechanisms of Achieving Self-Tolerance

Self-tolerance is achieved through several mechanisms, including central tolerance, which occurs during the development of immune cells in the thymus and bone marrow, and peripheral tolerance, which takes place in the body's tissues. Central tolerance eliminates self-reactive T and B cells, while peripheral tolerance involves regulatory T cells that suppress immune responses to self-antigens, ensuring that the immune system remains non-reactive to the body's own components.