basic of immunology

Basics of Immunology

Basics of Immunology

What is the immune system?

• Biological mechanism for identifying and destroying pathogens within a larger organism.

– Pathogens: agents that cause disease

• Bacteria, viruses, fungi, worms, etc.

• Types:

• Innate Immunity

• Adaptive Immunity

3

Immunity - Definition & Types

4

Adaptive Immunity

Innate Immunity• Definition:

• Resistance to infectious diseases and is

mediated by immune system

• Types:

• Innate or Non Specific

• Anatomic barriers: Skin, mucous

membrane

• Physiologic barriers: Temperature, pH

• Phagocytic Barriers:

• Inflammatory barriers: redness, swelling,

heat and pain

• Adaptive or Specific

• Antigen specificity

• Diversity

• Immunological Memory

• Self or non self recognition

Innate immunity

Adaptive Immunity - Types

6

• Naturally acquired Immunity

Arises as a result of accidental interaction

of a disease causing agent

• Artificially acquired Immunity

Immunity due to deliberate interaction of a

disease causing agent. e.g.., vaccination

The colors of the receptors indicate specificity: each can

bind to one specific antigen. Adaptive immunity can only

attack targets that it has prepared for

7

Active Passive Active Passive

Antigens enter the

body naturally;

body induces

antibodies and

specialized

lymphocytes

Antigens are

introduced by

vaccination; body

produces

antibodies and

specialized

lymphocytes

Antibodies pass

from mother to

fetus via placenta

or to infant via the

mother’s milk

Preformed

antibodies in

immune serum

are introduced by

injection

Adaptive Immunity

Naturally acquired Artificially acquired

Adaptive Immunity

Components of Immune System

8

• Cells

• Antigen presenting cells

• Polymorphic mono nuclear Leukocytes

• Cytotoxic leukocytes

• Natural Killer (NK) Cells

• Lymphokine activated Killers (LAK)

• Lymphocytes, B cells and T Cells

• Proteins

• Cytokines

• Antibodies

• Acute phase Reactants

• Antibodies

• Each B cell produces a specific type of antibody

• Antigen: Antibody Generator

• Any substance that can elicit an immune response

when administered parenterally

• Reacts with the antibody thus produced

Structure of Antibody

• Composed of 2 heavy and 2 light chains –

encoded by different genes

• Single disulfide bond between heavy and

light, two disulfide bonds between 2 heavy

chains.

• Light chain is either ƙ (kappa) or λ

(lambda); 98% of mouse antibodies are ƙ.

• Heavy chain constant region varies

depending on isotype.

9

Epitope – Paratope Interaction

Variable and constant regions are

encoded by different gene segments

• variable region binds antigen

• constant region binds receptors,

bacterial products, complement, etc.

10

Types of Antibodies - IgG

11

• Induced by protein antigens

• Constitutes about 80% of antibody in

serum

• Composed of two light chains (κ or λ)

and one type of heavy chain (γ)

• Coats Ag for its speedy uptake

• Four isotypes

• IgG1, IgG2, IgG3, IgG4

Most of BioGenex Antibodies are IgG Type

Types of Antibodies - IgA

12

• Constitutes 13% of total antibodies

• Predominant class of Ab in

extravascular secretions

• Present in saliva, tears, nasal secretions,

bronchial and digestive tract mucus and

mammary gland secretions

• Exists either as monomer or dimer

• Dimer is formed by two IgA monomers,

a J chain and secretory component

• Has two isotypes IgA1 and IgA2

Types of Antibodies - IgM

13

• Largest antibody

• Constitutes upto 8% of total Abs

• It is a pentamer formed by five

monomers of IgM Abs joined by

disulphide bridges

• First Ab that appears during immune

response

• Activates complement system

Types of Antibodies - IgD

14

• Membrane bound

• Constitutes less than 1% of total Abs

• Membrane bound and one of the main

receptors on mature B cells

• May play an important role in

regulation of immune responses.

Types of Antibodies - IgE

15

• Constitutes less than 0.003% of

total Abs

• Triggers allergies

• Binds to Mast cells and Basophils

• Subsequent exposure to the same

antigen triggers allergic reaction

• Responsible for release of factors

that attracts Eisonophils

Polyclonal vs. Monoclonal Antibodies

16

• Polyclonal Abs are produced from different

clones of B cells for a given Ag

• Recognizes the different epitopes on an Ag

• Monoclonal Ab are produced against a

single epitope


17

• Polyclonal Abs is produced from different

clones of B Lymphocytes and hence different

antibodies with distinct specificity for given

antigen (i.e same antigen different

epitopes).It’s robust, exhibit cross reactivity

• Monoclonal Abs is produced from a single

clone and directed against a single epitope.

It show lot to lot consistency and is specific

18


Monoclonal Polyclonal

Single plasma cell population /

single epitope Multiple epitopes

Higher Specificity Higher Sensitivity

Hybridoma technologyProduced in lab animals like Rabbit,

Goat, etc.

Lot to lot stability Lot to lot variations

Longer time to generate Cross Reactivity

Applications of Antibodies

• Western blotting: Detection of protein of interest in a mixture

• Flow cytometry: Detection of proteins in live cells

• ELISA: Binding characteristics of proteins and quantitation

• IHC: localization of proteins of interest with in a cell

• In situ Hybridization: detect modification and abnormalities at genetic level

19

Western IHC Direct Bind

ELISA

IP/ChIP Sandwich IF/Flow

Cytometry

Functional

Modulation

Denatyred/linear epitope folded/discontinuous epitope

Thank YouPlease visit www.biogenex.com for more details on our product portfolio

20

basic of immunology

Science