33. Regulation of the immune response. Immune tolerance. Mechanisms.

Question 1

Regulation of the immune response

Answer 1

3 layers of regulation.
1. Organismic- done by the nervous and endocrine system.
2. Systemic- done by the immune organs: bone marrow, thymus, spleen, lymph nodes
3. Molecular - synthesis of antibodies, antigen receptors of immunocompetent cells etc.

Question 2

Neuro-endocrine regulation

Answer 2

Suppression: Glucocorticoids, androgens, progesterone.
Enhancement: Estrogens, thyroxine, growth hormone, insulin.
Key Points:

Glucocorticoids: Used for immunosuppression (e.g., post-transplant), secreted under stress, increasing infection susceptibility.

Question 3

Role of the antibodies and other effectors

Answer 3

Inhibitory Fc-Receptors for IgG:
-Function: Inhibit B-cell activation when saturated.
-Signal: Indicates sufficient IgG antibodies are present.

Regulatory Mechanisms:
-Cancer Cell Impact: Malignant transformation leads to uncontrolled effector cell growth.
-Result: Suppresses normal cell development, causing immunodeficiency.

Question 4

Role of T-lymphocytes

Answer 4

Like all T lymphocytes, Treg cells originate from the thymus.

Function of Tregs:
-Block actions of some other types of lymphocytes, to keep immune system from being over-active.
-Maintain tolerance to self-antigens, and prevent autoimmune diease.

Question 5

Immune tolerance

Answer 5

Definition: Absence of immune response to accessible antigens.

Primary Focus: Tolerance of self-antigens

Nature: Acquired immunity, involving the entire immune system, not individual lymphocytes.

Mechanism: self-antigens recognized by their environment.

Immune tolerance is only reliable if the immune system is in continuous contact with the antigen.

Question 6

Types of immune tolerance. Mechanisms

Answer 6

1. Central Tolerance:

-Location: Central lymphoid organs (bone marrow, thymus).
-Mechanism: Autoreactive lymphocytes eliminated by apoptosis.
–B Cells: Receptor editing and negative selection in bone marrow.
–T Cells: Negative selection in thymus; stromal cells induce apoptosis in strongly autoreactive thymocytes.

2. Peripheral Tolerance:

-Purpose: Complements central tolerance; addresses self-antigens not handled centrally.
-Mechanism: Autoreactive T-cells become inactive if antigen is presented without B7 signal.
-T Regulatory Cells (Treg): Suppress overly strong or prolonged immune responses, inactivating T-helpers.