IgG & IgM Full Form

Introduction

Antibodies are formed in the bloodstream as a result of an infection's response. The immune system of the human body produces antibodies to get ready to neutralize any infection or foreign particle when it recognizes its existence. These proteins are also known as immunoglobulins (Ig). In this article, we will look at two types of immunoglobulins: IgM and IgG.

Table of Contents

1. Immunoglobulins

2. Structure of Immunoglobulins

3. Classification of Immunoglobulins

4. FAQs

Immunoglobulins

Immunoglobulins, often known as antibodies, are glycoprotein molecules generated by plasma cells (white blood cells). When the human body detects an antigen or a disease, B lymphocytes produce specialised proteins known as immunoglobulins. These Y-shaped blood proteins begin mitosis in order to multiply and attack foreign bodies. They play a crucial role in the immune response by selectively identifying and attaching to specific antigens, like viruses or bacteria, and assisting in their elimination.

Structure of Immunoglobulins

The structure, biological characteristics, distribution, and target specificity of the distinct immunoglobulin types and their subclasses (isotypes) set them apart from one another. For the selection and manufacture of antibodies as instruments for immunoassays and other detection applications, an understanding of immunoglobulin structure and classes is essential.

Each unit of the glycoproteins in immunoglobulins has four polypeptide chains: two identical light chains (L) and two identical heavy chains (H). These polypeptide chains have different amino acid compositions at their amino-terminal ends. The covalent interchain disulfide bonds and non-covalent interactions link the heavy and light chains together. This results in the formation of a Y-shape immunoglobulin structure that is bilaterally symmetrical. This Y-shape is divided into two regions: The bottom section is known as a constant region (C).

The two-arm top portion is known as the variable region (V). The constant region does not change from one antibody to the next, but the variable region does. Furthermore, the antibody's variable region binds to certain antigens and is known as the fragment of the antigen-binding (Fab) site.

The part of the antigen known as an epitope is the part that binds to the antigen-binding site.

The constant region is often the antibody's tail, also known as the fragment of crystallization (FC). It interacts with complement system receptor proteins or attaches to the surface of immune cells.

Every L chain has one variable domain VLand one CL constant domain. The H chains contain a variable domain, VH, as well as three constant domains: CH1, CH2, and CH3. Each heavy chain contains roughly twice as many amino acids and has a higher molecular weight (50,000) than each light chain (25,000). As a result, the molecular weight of the immunoglobulin monomer as a whole is about 150,000.

The antigen-binding sites of immunoglobulin (Ig) molecules are located in the V regions of both the H and L chains. Therefore, each Ig monomer is bivalent and has two antigen-binding sites. The hinge region is formed by disulfide connections between the first and second C region domains of the H chains. IgG, IgA, and IgD all contain this flexible hinge region, but IgM and IgE do not. It is responsible for the variable distance between the two antigen-binding sites.

Classification of Immunoglobulins

Immunoglobulins is classified into five categories on the basis of the type of heavy chain found in the molecule:

1. Immunoglobulin M or IgM - These have mu-chains.

2. Immunoglobulin G or IgG - These have gamma chains.

3. Immunoglobulin A or IgA - These have alpha chains.

4. Immunoglobulin D or IgD - These have delta chains.

5. Immunoglobulin E or IgE - These have epsilon chains.

These immunoglobulins can work in specific types of immunological responses and at specific stages of the immune response due to variations in heavy-chain polypeptides. The polypeptide protein sequences in the Fc fragment are principally responsible for these variations.