Introduction

Antibodies, also known as immunoglobulins, are a class of proteins that play a critical role in the immune response. They are produced by B-lymphocytes and are able to specifically bind to a wide variety of antigens. In this text we will discuss about the structure of antibodies.

Basic Structure

Antibodies have a basic structure that consists of four polypeptide chains: two heavy chains and two light chains.

Each heavy chain is composed of a variable domain (VH) and a constant domain (CH).

Each light chain is composed of a variable domain (VL) and a constant domain (CL).

The variable domains of the heavy and light chains form the antigen-binding site of the antibody, while the constant domains play a role in the effector functions of the antibody.

Variable Domains

The variable domains of the heavy and light chains are responsible for the specificity of the antibody for a particular antigen.

The variable domains are composed of three hypervariable regions, also known as complementarity-determining regions (CDRs), and four framework regions (FRs).

The CDRs are responsible for the formation of the antigen-binding site and are highly variable, while the FRs are more conserved.

Constant Domains

The constant domains of the heavy and light chains are responsible for the effector functions of the antibody, such as complement activation, opsonization, and neutralization.

The constant domains are further divided into several subclasses, including IgG, IgM, IgA, IgD, and IgE, each with distinct properties and functions.

Quaternary Structure

The quaternary structure of antibodies refers to the arrangement of the heavy and light chains in the three-dimensional space.

The basic structure of antibodies is a Y-shaped tetramer, in which the variable domains of the heavy and light chains form the arms of the Y, while the constant domains form the stem of the Y.

Conclusion

Antibodies are a class of proteins that play a critical role in the immune response.

Antibodies have a basic structure that consists of four polypeptide chains: two heavy chains and two light chains.

The variable domains of the heavy and light chains are responsible for the specificity of the antibody for a particular antigen.

The constant domains of the heavy and light chains are responsible for the effector functions of the antibody.

The quaternary structure of antibodies refers to the arrangement of the heavy and light chains in the three-dimensional space.