Detailed Antibody Structure (FL-Immuno/35)

Summary

This video lecture explores the role of B lymphocytes in humoral immunity. It explains how B cells, originating and maturing in the bone marrow, recognize antigens through B cell receptors, leading to activation and differentiation into plasma and memory cells. Plasma cells produce antibodies, which are glycoproteins that bind to pathogens, facilitating their destruction. The lecture details the structure of antibodies, including light and heavy chains, variable and constant regions, and hypervariable regions (CDRs) responsible for antigen binding. The different types of light and heavy chains and their molecular structure are also discussed.

Takeaways

• 😀 B lymphocytes are responsible for humoral immunity, which protects against extracellular pathogens.
• 😀 B lymphocytes originate and mature in the bone marrow before being released into the blood and circulating through lymphoid tissues.
• 😀 B cells recognize specific antigens through B cell receptors (BCRs), which are membrane-bound immunoglobulins.
• 😀 Upon activation, B cells proliferate and differentiate into plasma cells (antibody-secreting cells) and memory B cells.
• 😀 Antibodies, also known as immunoglobulins, are glycoproteins that are produced and secreted by plasma cells.
• 😀 Antibodies have a Y-shaped structure with two antigen-binding sites and an FC region (stem).
• 😀 The hinge region of the antibody allows flexibility, enabling it to adapt to different spatial arrangements of antigens.
• 😀 Each antibody consists of two identical heavy chains and two identical light chains, connected by disulfide bonds.
• 😀 There are two types of light chains in humans: Kappa and Lambda, which are encoded by different chromosomes.
• 😀 The antigen-binding sites of antibodies are formed by variable regions on both the heavy and light chains, which have hypervariable regions (CDRs) that are complementary to the antigen.
• 😀 The constant regions of the antibody vary between different classes of antibodies and are responsible for the classification of antibodies into five types (IgG, IgA, IgM, IgD, IgE).

Q & A

What is the main difference between cell-mediated immunity and humoral immunity?

Cell-mediated immunity, involving T-lymphocytes, fights against intracellular pathogens, such as infected or tumor cells. Humoral immunity, involving B-lymphocytes, targets pathogens that reside in extracellular spaces by producing antibodies.

Where do B lymphocytes originate and mature?

B lymphocytes originate and complete their maturation in the bone marrow.

What happens when B cells recognize a specific antigen?

When B cells recognize a specific antigen, they get activated, proliferate, and differentiate into effector B cells (plasma cells) and memory B cells.

What is the role of plasma cells in immunity?

Plasma cells are effector B cells that secrete antibodies specific to the recognized antigen, helping neutralize or eliminate the pathogen.

What are antibodies and how do they function?

Antibodies are glycoproteins also known as immunoglobulins. They are Y-shaped molecules with two antigen-binding sites that bind to pathogens or antigens to activate defense mechanisms for pathogen destruction.

What is the structure of an antibody molecule?

An antibody molecule consists of four polypeptide chains: two identical heavy chains (longer) and two identical light chains (shorter). These chains are connected by disulfide bonds and form a Y-shaped structure.

What is the function of the hinge region in an antibody molecule?

The hinge region provides flexibility to the antibody molecule, allowing it to adjust to different spatial arrangements of antigens, facilitating the binding to diverse antigens or epitopes.

How do carbohydrate chains influence the antibody structure?

Carbohydrate chains attached to the heavy chains increase the solubility of the immunoglobulin and play a role in its overall function.

What is the significance of the variable and constant regions in antibody structure?

The variable regions (in both light and heavy chains) are responsible for antigen binding, while the constant regions maintain structural stability and contribute to classifying antibodies into different types.

What is the role of complementarity determining regions (CDRs) in antibodies?

CDRs are hypervariable regions in the variable regions of both the light and heavy chains. They form the antigen-binding sites and determine the specificity of the antibody for a particular antigen.