UNIT 5

ImmunoBiology

• Elements of the immune system,

• Types of the immune response
• Active and passive immunity
• Immunoinformatics
• epitope prediction tools
 INTRODUCTION

IMMUNOBIOLOGY : ImmunoBiology is the study of

the immune system's physiological reactions and
biological aspects of immunity to disease
IMMUNITY : Immunity is the ability of the
body to protect against all types of foreign
bodies like bacteria, virus, toxic substances
which enter the body.
Immunity is done by immune system which is a
complex network of Lymphoid organs such as
Bone marrow, thymus, Spleen etc.,
Eukaryotic Cells, Bacteria, and Viruses
Body Defence system
 Body Defenses: Overview
● Physical barriers: skin & epithelial linings & cilia
● Chemical: acids, mucous & lysozymes
● Immune defenses – internal
● Innate, non-specific, immediate response (min/hrs)
● Acquired – attack a specific pathogen (antigen)
● Steps in Immune defense
● Detect invader/foreign cells
● Communicate alarm & recruit immune cells
● Suppress or destroy invader
 Discrimination of self from non-self
“The success of the immune system depends on its
ability to discriminate between foreign (nonself) and
host (self) cells. Survival requires both the ability to
mount a destructive immune response against
nonself and the inability to mount a destructive
response against self.”
 Markers of Self
Epithelia Muscle cell
l
cell

Nerve
Leukocyte
cell

At the heart of the immune response is the ability to distinguish

between “self” and “non-self.”
• Every cell in your body carries the same set of distinctive
surface proteins that distinguish you as “self.”
• Normally your immune cells do not attack your own body
tissues, which all carry the same pattern of self-markers; rather,
your immune system coexists peaceably with your other body
cells in a state known as self-tolerance.

This set of unique markers on human cells is called the major

histocompatibility complex (MHC) proteins.
 Markers of Non-self

Bacteria SARS virus

Non-self leukocyte Epitop

Non-self nerve cell e
Antigen

Antigen = any non-self substance

• Virus
• Bacteria
• Non-self cell (foreign cell)

Epitope = The distinctive markers on antigens that trigger an

immune response
 Blood
●Blood is 55% liquid (plasma) and 45% cellular

●Cellular component of blood:

●Red blood cells = carry oxygen
●White blood cells = immune system
●Platelets = clot blood Stem Cell

●All blood cells arise from a

pluri-potent stem cell found
in bone marrow
Blood
cells

Red Blood
cells White blood cells (immune
cells)
Platelets
Leukocytes in the Blood

Red Blood Cells 5.0 X 106/mm3

Platelets 2.5 X 105/mm3

Leukocytes 7.3 X 103/mm3

1 Neutrophil 50-70%

2 Lymphocyte 20-40%

3 Monocyte 1-6%

4 Eosinophil 1-3%

5 Basophil <1%
Neutrophil
 Eosinophil
• 1-3 % of WBC
• Help control allergic reactions
• Release an enzyme histamine – a chemical
released during allergic reactions
 Basophil
• Less than 1% of WBC
• Involved in allergic and inflammatory reactions
• Contains large amounts of histamines which may
be released in injured tissue in order to increase
inflammation
• Contains heparin an anti-clotting chemical
 Lymphocytes

• 30% of all leukocytes

• Made from stem cells, but are released from
lymph nodes, thymus, spleen and bone marrow
• Produce antibodies and destroy foreign cells
found in infectious mononucleosis
 Monocyte
• 6% of WBC’s
• Enter connective tissue
• Eat bacteria, dead cells and other littering tissue
 Organs of the Immune System

Tonsils and adenoids

Lymph nodes
Lymphatic vessels
Thymus
Lymph nodes

Spleen

Peyer’s patches
Appendix
Lymph nodes
Bone marrow Lymphatic vessels

Bone marrow, the soft tissue in the hollow center

of bones, is the ultimate source of all blood cells,
including the immune cells.
 Lymphatic System
The organs of your immune system are connected
with one another and with other organs of the body by
a network of lymphatic vessels.
 Lymphatic System
The organs of your immune system are connected
with one another and with other organs of the body by
a network of lymphatic vessels.
1. Lymphatic vessels closely
parallels the body’s veins and
arteries
- Lymphatic vessels carry lymph,
a clear fluid that bathes the
body’s tissues

- Cells/fluids are exchanged

between blood and lymphatic
vessels, enabling the
Lymph node lymphatic system to monitor
Lymphatic vessel the body for invading
microbes.
2. Lymph nodes contain high levels
of immune cells
 Nonspecific Defenses, Phagocytes
● Remove cellular debris and
respond to invasion by foreign
pathogens
● Monocyte-macrophage system -
Fixed and free
● Microphages – Neutrophils and
eosinophils
● Move by diapedesis
● Exhibit chemotaxis
 Phagocytosis is a process wherein a cell binds to the item it
wants to engulf on the cell surface and draws the item inward
while engulfing around it.
The process of phagocytosis
often happens when the cell is trying to destroy something, like
a virus or an infected cell, and is often used by immune system
cells.
 Nonspecific Defenses, Immunological surveillance

● Constant monitoring of normal tissue by NK cells

● NK cells
● Destroy cells with foreign antigens
Recognize cell surface markers on foreign cells
● Natural Killer(NK) Cells : Properties and Function
● Natural killer(NK) cells are large granular lymphocytes.
They are Non-phagocytic cells. The granules of natural killer
cells contains preformed biologically potent molecules.
• The concentration of NK cells of total Lymphocytes is 5%
to 10%.
• Some of these molecules has capability to form pores in the
membrane of target cells, Resulting in the lysis of the cell.
• Some other molecules induce apoptosis of the target cell.
 Inflammation
● A normal part of the body's response to injury or
infection.
Inflammation
occurs when the body releases chemicals that trigger an
immune response to fight off infection or heal damaged
tissue. Once the injury or
infection is healed, the inflammatory process ends.
Inflammation: Tissue damage to Tissue Repair

Diabetic foot ulcer

Adaptive or Acquired
Immunity
●Acquired after
birth
●Seen only in
vertebrates
●Characteristic
features are:
●Diversity
●Specificity
●Self vs non-self
●Memory
 Immune Response
System
Made up of two cellular systems (lymphocytes)
1. Humoral immunity - B cells
2. Cell-mediaed immunity - T cells

B cells make
antibodies

T cells mount
direct attack on
foreign/infected
cell
 Cell mediated immunity
● T cells must be activated
● Must have both surface antigen recognition and costimulation to activate
● T cell receptors recognise and bind to specific antigen presented with MHC
complexes
● T cell only activated if binds to antigen and receives costimulation
● Co-stimulation provided by cytokines or membrane proteins
● Need for co-stimulation prevents immune responses occurring accidentally
● Recognition (binding to receptor) without costimulation results in anergy (prolonged
state of inactivity) in both B and T cells
● Once T cell co-stimulated it is activated
● Proliferates
● Differentiates (forms more highly specialised cells)
● Activation, proliferation and differentiation occurs in secondary lymphatic
organs and tissues
 Humoral (Antibody-mediated) immunity
● Mediated by B cells
● Antigen can activate B cell in
two ways:
● direct binding
●provokes less vigorous response
● B cells process antigen (act as APC)
and display processed antigen with
MHC proteins
● TH cells recognise processed antigen
● TH cells provide co-stimulation for
B cell
● Activated B cell
● proliferates and differentiates
● plasma cells
● secrete antibodies with same
antigen binding properties as
receptors
● memory B cells
 Active and Passive Immunity
●Active immunity and passive
immunity are two types of acquired
immunity.
Immunity: Active and Passive
 VACCINES
• Vaccination is the administration of antigenic agents applied to
stimulate the immune system of an individual and to develop
adaptive immunity to a disease.
• Vaccines can ameliorate, or often even prevent, the effects of
infection. Vaccination is generally considered to be the most
effective method of preventing infectious diseases
• A multi-stage tuberculosis vaccine and Covid has recently been
developed to confer protection after the exposure to the pathogen .
There are numerous vaccine examples, including experimental ones
against AIDS, cancer and Alzheimer's disease.
• The core mechanism behind all the vaccinations is the ability of the
vaccine to initiate an immune response in a quicker fashion than
the pathogen itself.

• The purpose of every vaccination is to present a particular antigen

or set of antigens to the immune system in order to evoke a
relevant immune response.

• The main active component of a vaccine may be inactive, but still

intact (attenuated bacteria or viruses), or purified components of
the pathogen that are known to induce immune reaction.
 Types of Vaccines
1. Inactivated vaccines
●This type of vaccine consists of virus particles grown in cell
culture and inactivated by applying high temperature or
chemicals such as formaldehyde. Booster shots required Eg.,
Hepatitis A, Polio,Flu
2. Live attenuated vaccines
●The attenuated vaccines contain live virus particles with low
levels of virulence. They have retained their ability to slowly
reproduce, and thus they remain a continuous source of
antigen for a certain period after the first vaccination,
reducing the need of booster shots. Eg., MMR combined
vaccine, Small pox, Rotavirus
3. Subunit vaccines
●Subunit vaccines use only the antigenic components that
best stimulate the immune system, instead of dealing with the
entire micro-organism.Eg., Hepatitis B,HPV (Human
papillomavirus), Pertusis
4.Toxoid vaccines
●The toxoid vaccines are typical solution for bacteria that
secrete harmful metabolites or toxins. It is common to use
them when the main reason for discomfort or sickness is a
bacterial toxin. Eg., diphtheria and tetanus.
5. DNA vaccines
●DNA vaccination is a very new approach for induction of
humoral and cellular immune responses to protein antigens by
administering genetically engineered DNA. DNA vaccines are
still in the experimental stage, and have been tested in
numerous viral, bacterial and parasitic models of disease
6. Peptide vaccines
●The improved knowledge of antigen recognition at molecular
level has contributed to the development of rationally
designed peptide vaccines. chemical approach to synthesize
the identified B-cell and T-cell epitopes that are
immunodominant and can induce specific immune responses.
The peptide vaccines against various cancers have been
developed, and entered phase I and phase II of clinical trials
 Vaccines yet to developed!

Malaria-parasitic disease
HIV/AIDS Patient Aging

Diabetes Rheumatoid arthritis

Smoking causes cancer
 Immune Engineering
● The complexity of the
immune system can be
compared to that of the
brain.
● There is a vast number of
cells, molecules, and
organs that compose the
immune system, and these
have to act in concert, and
together with other vital
systems, so as to promote
and maintain life.
● Neither can the immune
system act in isolation to
maintain life, nor can a
higher organism live
without an immune
system.
● Artificial immune systems (AIS) compose a new
computational intelligence approach inspired by
theoretical and experimental immunology with
applications to problem solving.

● Like all new approach, the field still lacks a more

formal description and better theoretical foundations.

● The application of mathematical analysis and modeling

to immunology may result in outcomes such as a deeper
and more quantitative description of how the immune
system works, a more critical analysis of hypothesis, it
can assist in the prediction of behaviors and the design
of experiments.
• Immuno-informatics

• Epitope prediction tools

Summary of Acquired Immunity
 T-cell epitopes

●T-cell epitopes are presented on the

surface of an antigen-presenting cell
(APC), where they are bound to
major histocompatibility (MHC)
molecules in order to induce immune
response
● MHC class I molecules usually
present peptides between 8 and 11
amino acids in length, whereas the
peptides binding to MHC class II may
 T cell Epitope Prediction Methods
● Binding affinity predictions for a range of MHC
molecules is considered to be the most popular
epitope prediction methods.
● Molecular binding between antigenic peptides and
MHC molecules is necessary for recognition by
cytotoxic T-cells.
● The peptides with ability to bind MHC molecules
could be predicted by different methodologies
including Hidden Markov model (HMM), Artificial
neural networks (ANNs), Support Vector Machine
(SVM), and Quantitative matrices.
https://services.healthtech.dtu.dk/service.php
?NetMHCpan-4.1
 B-cell epitope prediction
● Mapping B-cell epitopes within the protein sequence
of antigens plays a crucial role in vaccine design,
immunodiagnostic design and immunogen design for
antibody production efforts
● B-cell epitopes are determinant regions of the antigen
with the ability to bind immunoglobulins and B-cell
receptors (BCRs).
● Identification of B-cell epitopes capable of invoking
strong immune responses plays a pivotal role in
effective vaccine designing efforts
 BepiPred
●BepiPred-2.0 is based on a random forest
algorithm trained on epitopes annotated from
antibody-antigen protein structures.
● This new method was found to outperform
other available tools for sequence-based
epitope prediction both on epitope data
derived from solved 3D structures, and on a
large collection of linear epitopes downloaded
from the IEDB database
https://services.healthtech.dtu.dk/service.php?BepiPred-2.0
THANK YOU