IMMUNOGLOBULINS G- STRUCTURE OF IgG MOLECULE

Structure of IgG Molecule

1. IMMUNOGLOBULINS STRUCTURE OF HUMAN IgG MOLECULE

2. CONTENTS What are immunoglobulins? Physical characteristics of immunoglobulin molecule Structure of immunoglobulin molecule Classes of immunoglobulins Chemical structure of Human IgG molecule IgG Subclasses Role of IgG in human immune response Multiple Myeloma

3. The defense strategies of the body are collectively referred to as immunity. Molecules which are responsible for immune function of the body are termed as immunoglobulin. Immunoglobulin , specialized group of proteins mostly associated with gamma-globulin of plasma protein . Immunoglobulins are glycoprotein molecules. WHAT ARE IMMUNOGLOBULINS?

4. Immunoglobulin molecule consists of two heavy chains and two light chains: Heavy chains(H) : Molecular Weight(53,000 to 75,000 each) Light chains(L) : Molecular Weight(23,000 each) AMINO ACIDS Heavy chains : 450 amino acids each Light chains : 212 amino acids each PHYSICAL CHARACTERISTICS OF IMMUNOGLOBULIN MOLECULE

5. Immunoglobulin is a Y-shaped tetramer.( H 2 L 2 ). Heavy chains of immunoglobulin are linked with carbohydrates so often called GLYCOPROTEIN . Both heavy and light chains of immunoglobulin has two regions(domains) : Constant Variable Specificity of immunoglobulin molecule is due to variable regions in heavy and light chains . STRUCTURE OF IMMUNOGLOBULIN MOLECULE

6. The variable and constant regions differ with respect to heavy and light chains. HEAVY CHAIN Constant: Three quarters of amino acid terminal is constant(C H1 ,C H2 ,C H3 ) Variable: One quarter of amino acid terminal is variable(V H ) LIGHT CHAIN Constant: Amino terminal half of light chain(C L ) Variable: Carboxy terminal half of light chain(V L ) STRUCTURE OF IMMUNOGLOBULIN MOLECULE

7. BASIC STRUCTURE OF IMMUNOGLOBULIN MOLECULE

8. Humans have five classes of immunoglobulins depending on the type of heavy chain present in them. Five types of antibodies are IgG,IgA,IgM,IgE,IgD-containing heavy chains Two types of light chains are present-namely kappa and lambda. CLASSES OF IMMUNOGLOBULINS

9. TYPE H-CHAIN STRUCTURE FUNCTION IgG γ CHAIN Y-SHAPED MONOMER MOSTLY RESPONSILE FOR HUMORAL IMMUNITY IgA α CHAIN MONOMER OR DIMER PROTECTS THE BODY SURFACE IgM µ CHAIN PENTAMER HUMORAL IMMUNITY AND SERVES AS THE FIRST LINE OF DEFENSE IgD δ CHAIN Y-SHAPED MONOMER B-CELL RECEPTOR IgE ε CHAIN Y SHAPED MONOMER HUMORAL SENSITIVITY AND HISTAMINE RELEASE CLASSES OF Ig

10. TYPES OF IMMUNOGLOBULINS

11. CHEMICAL STRUCTURE AND FUNCTIONS OF HUMAN IMMUNOGLOBULIN G(IgG) MOLECULE

12. DIGRAMATIC REPRESENTATION OF HUMAN I gG

13. IgG antibodies are large molecules of about 150 kDa made of four polypeptide chains. It contains two identical class Y heavy chains of about 50 kDa and two identical light chains of 25 kDa. Linkages present between the chains are disulphide linkages. STRUCTURE OF HUMAN IgG MOLECULE

14. There are four IgG subclasses described in human, mouse and rat. They differ in the number of disulphide bonds and the length and flexibility of the hinge region. The four subclasses are as follows: IgG1 : Comprises 60-65% of main IgG subclass and ,mainly responsible for thymus mediated immune response against proteins and polypeptide antigens. IgG SUBCLASSES

15. IgG2 : Comprises20-25% of the main subclass and is prevalent immune response against carbohydrate-/polysaccharide antigens. IgG3 : Comprises around 5-10% of total IgG and plays a major role in immune response against protein or polypeptide antigens. IgG4 : Comprises usually less than 4% of total IgG. It does not bind to polysaccharides and precise role is mostly unknown. IgG SUBCLASSES

16. SUBCLASSES OF HUMAN IgG

17. Major immunoglobulin in blood, lymph fluid, cerebrospinal fluid and peritoneal fluid. It is a key player in humoral immune response. Serum IgG in healthy humans presents approximately 15% of total proteins beside albumins, enzymes, and other globulins and many more. ROLE IN IMMUNE RESPONSE

18. A plasma cell cancer constitutes 1%of all cancers affecting the population. Occurs due to malignancy of a single clone of plasma cells in bone marrow. This results in overproduction of abnormal immunoglobulins mostly IgG and in some cases IgG or IgM. Often leads to Amyloidosis i.e. deposits of light chain fragments in tissues (liver, kidney , intestine. MULTIPLE MYELOMA

19. THANK YOU