Immunoglobulins and Their Functions

Study Notes

Immunoglobulins, also known as antibodies, are proteins produced by plasma cells.
They play a crucial role in the immune system.
They are Y-shaped molecules with two heavy chains and two light chains.
Variability in the amino acid sequences of the variable regions allows them to recognize a vast array of antigens.
Each immunoglobulin molecule consists of four polypeptide chains (2 heavy and 2 light chains).
They have both constant and variable regions.
They are linked by disulfide bonds.
They have antigen-binding sites (also known as hypervariable regions).
They are divided into Fc and Fab regions.

Neutralization: Bind to pathogens or toxins, preventing them from interacting with host cells.
Opsonization: Coat pathogens, marking them for destruction by phagocytes.
Complement Activation: Trigger the complement system, leading to the lysis of pathogens
Agglutination: Clump pathogens together, making them easier to eliminate
Antibody-Dependent Cellular Cytotoxicity (ADCC): Bind to infected cells, marking them for destruction by immune cells like natural killer (NK) cells.

In opsonization, antibodies bind to antigens on the pathogen's surface.
The Fc region of the antibody interacts with Fc receptors on phagocytes.
This enhances the ability of the immune cells to engulf and destroy the pathogen.

It is a mechanism where immune cells can kill target cells that are coated with antibodies.
Antibody Binding: IgG antibodies bind to specific antigens on target cells (e.g., virus-infected or tumor cells).
Fc Receptor Engagement: Immune effector cells (like NK cells, macrophages, and neutrophils) express Fc receptors that bind to the Fc region of the antibodies.
Cell Activation: Binding triggers the activation of effector cells, leading to the release of cytotoxic granules or pro-inflammatory cytokines.
Target Cell Destruction: Perforin forms pores in the target cell membrane, allowing granzymes to enter and induce apoptosis.