1. SPECIFIC HOST RESISTANCE &THE
PRACTICAL ASPECTS OF IMMUNITY
ADELABU O.A

2. OUTLINE
•Definition of key words
•Antibodies
•Immunity &its types
•Immune response
•Antigens
•Immunization
•vaccination

3. Specific host resistance: Ability
of an organism(host) to
recognize and defend itself
against specific pathogens or
antigens(foreign).
PRACTICAL ASPECTS OF
IMMUNITY

4. Specific host resistance
• is triggered when a pathogen evades the innate
immune system and generates a threshold level of
antigen and generates "stranger" or "danger" signals
activating dendritic cells.
The major functions of the acquired immune system
include:
• the recognition of specific "non-self" antigens in the
presence of "self", during the process of antigen
presentation.
• the generation of responses that are tailored to
maximally eliminate specific pathogens or pathogen-
infected cells.
• the development of immunological memory, in which
each pathogen is "remembered" by a signature
antibodies or T cell receptors, this is also known as the
"anamnestic response". These memory cells can be

5. specificity
• T cells compare non-self antigens to HLA
(human leukocyte antigens) molecules
• Antigens can be proteins, polysaccharides or
glycoproteins components of pathogens
• An antigen announces its foreignness by
means of intricate and characteristic shapes
called epitopes, which protrude from its surface.
Most antigens, even the simplest microbes,
carry several different kinds of epitopes on their
surface; some may carry several hundred.
However, some epitopes will be more effective
than others at stimulating an immune response.

6. Specific host resistance
• its remarkable ability to distinguish
between the body’s own cells,
recognized as “self,” and foreign
cells, or “nonself.”
• The body’s immune defenses
normally coexist peacefully with
cells that carry distinctive “self”
marker molecules. But when
immune defenders encounter
foreign cells or organisms carrying
markers that say “nonself,” they
quickly launch an attack.
• Anything that can trigger this
immune response is called an
antigen

8. Antibodies
Proteins that recognize and bind to a
particular antigen with very high
specificity.
Made in response to exposure to the
antigen.
One virus or microbe may have several
antigenic determinant sites, to which
different antibodies may bind.
Each antibody has at least two identical
sites that bind antigen: Antigen binding
sites.
Valence of an antibody: Number of antigen

9. ANTIBODY STRUCTURE

10. Immunoglobulin Classes
I. IgG
Structure: Monomer
Placental Transfer: Yes
Known Functions: Enhances phagocytosis,
neutralizes toxins and viruses, protects fetus
and newborn.
II. IgM
Structure: Pentamer
Known Functions: First antibodies produced
during an infection. Effective against
microbes and agglutinating antigens.

11. Immunoglobulin Classes
III. IgA
Structure: Dimer
Known Functions: Localized protection of mucosal
surfaces. Provides immunity to infant digestive tract.
IV. IgD
Structure: Monomer
Known Functions: In serum function is unknown. On B
cell surface, initiate immune response.
V. IgM
Structure: Pentamer
Known Functions: First antibodies produced during an
infection. Effective against microbes and agglutinating
antigens.

12. Monoclonal antibodies
A substance, usually a protein, which can be
synthesised in the laboratory in pure form by
a single clone of cells.
Detect only one epitope on the antigen.
Polyclonal antibodies
The immune response to an antigen
generally involves the activation of multiple
B-cells all of which target a specific epitope
on that antigen.
Recognise multiple epitopes on any one
antigen

13. Specific immunity
• Occurs as the result of prior exposure to an
infectious agent or its antigens. It is sub-divided
into natural and artificial immunity.
• Natural immunity – occurs through contact with
a disease causing agent, where the contact was
not deliberate.
• Artificial immunity – is produced by deliberate
exposure to an antigen, as in vaccination.

14. Natural immunity
Passive(maternal) – is acquired by the
neonate by transplacental transfer of
immunoglobulins or from ingestion of
colostrum.
Active(infection) – follows an exposure to
an antigen; where adaptive immunity
occurs.
Artificial immunity
Passive(antibody transfer) – the transfer of
antibodies from a donor in which they were
produced to a recipient for temporary
immunity.
Active(immunization) – stimulation with

15. Humoral immunity – is mediated by secreted
antibiotics, where the protection provided by
cell mediated immunity involves T-
lymphocytes alone.
Passive – antibodies are transferred
between individuals, the T-cells come from
another organism.
Active – organisms generates its own
antibiotics, the T-cells are stimulated.

16. Figure 1: Divisions of immunity

17. Types of immunity
Innate(non-specific) immunity
It is the basic resistance to disease that a
species possesses, it is the first line of
defense against infection
Adaptive (acquired) immunity
Is the adaptive immune system, also
known as specific immune system that is
composed of highly specialized, systemic
cells and processes that eliminate or
prevent pathogenic growth.

18. Adaptive(acquired)
immunityPassive immunity – is the protection by
products produced by an animal or human
and transferred to another human, usually
by injection, it is effective but it doesn’t last
long(few week or months).
Active immunity – is the protection that is
produced by the person’s own immune
system, is usually permanent.

19. Immune Response
• Immune response is the reaction of the
body’s cells and fluids to the presence of a
substance unknown to the body and its
components
• The immune system recognizes and destroys
substances that contain antigens, in this way
the body is protected from possibly harmful
substances

20. • Antigens are substances(usually
proteins) on the cell surface or non living
substances such as toxins, drugs and
foreign particles
• HLA antigens is a group of antigens that
the immune system sees as normal and
usually doesn’t react against them. HLA
are proteins of the body’s cells.

21. Primary and Secondary
Response
• Primary immune response is what happens
when the body is first exposed to a
pathogen or an unwanted substance, the T-
helper is triggered.
• Secondary response is triggered on
subsequent infections, the body being
invaded keeps memory B and T cells and
has antibodies for the antigen.

22. B cells and T cells
• B cells also called B lymphocytes are
produced and mature in the bone marrow
• B cells are essential components of
Adaptive immunity and play a large role
in the humoral immune response
• B cells make antibodies against antigens,
perform the role of APCs and develop
into memory B cells after activation by
antigen interaction

23. • On the other hand, the precursors of T
cells leave the bone marrow and mature
in the thymus
• T cells play a central role in cell-mediated
immunity
• T cells have a special receptor on their
cell surface called T cell receptors (TCR)

24. Antigens and Immunogens
• All immunogens are antigens but not all
antigens are immunogens
• Immunogen is any agent capable of
inducing an immune response, it
activates the immune system cascade
• While antigen is any agent that binds to
components of the immune response-
lymphocytes and their receptors-
antibodies and the TCR

25. Immunization
• Immunization, or immunisation, is the process
by which an individual's immune
system becomes fortified against an agent.
• When this system is exposed to molecules that
are foreign to the body, called non-self, it will
orchestrate an immune response, and it will
also develop the ability to quickly respond to a
subsequent encounter because
of immunological memory.

26. Cont…
• The most important elements of the immune
system that are improved by immunization are
the T cells, B cells, and the antibodies .
• Memory B cells and memory T cells are
responsible for a swift response to a second
encounter with a foreign molecule.
• Immunizations are less risky and an easier
way to become immune to a particular disease
than risking a milder form of the disease itself.
They are important for both adults and children
in that they can protect us from the many
diseases out there

27. Immunological memory

28. Active immunization
• Active immunization is the induction of immunity after
exposure to an antigen. Antibodies are created by
the recipient and may be stored permanently.
• Active immunization can occur naturally when a
microbe or other antigen is received by a person who
has not yet come into contact with the microbe and
has no pre-made antibodies for defence. The
immune system will eventually create antibodies for
the microbe, but this is a slow process and, if the
microbe is deadly, there may not be enough time for
the antibodies to begin being used.

29. Artificial active immunization
• It is when the microbe is
injected into the person
before they are able to take
it in naturally.
• The microbe is treated, so
that it will not harm the
infected person.
Depending on the type of
disease, this technique
also works with dead
microbes, parts of the
microbe, or treated toxins
from the microbe.

30. Passive immunization
• it is when pre-synthesized elements of
the immune system are transferred to a
person so that the body does not need to
produce these elements itself.
• Currently, antibodies can be used for
passive immunization. This method of
immunization begins to work very quickly,
but it is short lasting, because the
antibodies are naturally broken down,
and if there are no B cells to produce
more antibodies, they will disappear.

31. Artificial passive immunization
It is a short-term
immunization which is
achieved by the
transfer of human (or
animal) antibodies
specific for a pathogen
to non-immune human
or animal. It is used
when there is a high
risk of infection and the
body has no sufficient
time to develop its own
immune response

32. Vaccination
• it is the administration of antigenic material
(a vaccine) to stimulate an individual's immune
system to develop adaptive immunity to
a pathogen.
• Vaccines can prevent or
ameliorate morbidity from infection. The active
agent of a vaccine may be intact but inactivated
(non-infective) or attenuated (with reduced
infectivity) forms of the causative pathogens, or
purified components of the pathogen that have
been found to be highly immunogenic (e.g.,
outer coat proteins of a virus).

33. Early tissue and Cell Culture in
vaccine Development
•In order to develop vaccines
that could be mass-produced,
researchers first had to grow
the viruses or bacteria with
which to develop those
vaccines in large quantities
and with great consistency.
• Compared with bacteria,
which can be grown in a
laboratory environment when
placed in a suitable growth
medium, viruses cannot
reproduce on their own and
require living cells to infect.
After a virus infects a cell, it
uses the cell’s own
components to produce more
copies of itself.

34. Types of vaccines
Inactivated vaccine
– It consists of virus or bacteria that are grown In
culture and then killed, using a method such
as heat or formaldehyde. E.g Polio vaccine and
Hepatitis A vaccine
– Although the virus or bacteria particles are
destroyed and cannot replicate, the
virus capsid proteins or bacterial wall are intact
enough to be recognized and remembered by
the immune system and evoke a response.
When manufactured correctly, the vaccine is
not infectious, but improper inactivation can
result in intact and infectious particles.

35. Attenuated vaccine
– live virus or bacteria with very low virulence are
administered. They will replicate, but very slow.
Since they do reproduce and continue to
present antigen to the immune system beyond
the initial vaccination, boosters may be required
less often.
– These vaccines may be produced by
passaging, for example, adapting a virus into
different host cell cultures, such as in animals,
or at suboptimal temperatures, allowing
selection of less virulent strains, or by
mutagenesis or targeted deletions in genes
required for virulence.e.g Measles, mumps,
rubella (MMR combined vaccine) Varicella
Types of vaccines

36. SUBUNIT AND CONJUGATE VACCINES
Both subunit and conjugate vaccines contain only
pieces of the pathogens they protect against.
Subunit vaccines use only part of a target
pathogen to provoke a response from the immune
system.
This may be done by isolating a specific protein
from a pathogen and presenting it as an antigen on
its own. Examples are acellular pertussis vaccine
and influenza vaccine
,Meningococcal,Pneumococcal,influenza(injection)
,Hepatitis B.

37.  A preventative vaccine is administered to a person
who is free of the targeted infection. By introducing a
part of the virus or an inactive virus into the body, the
immune system reacts by producing antibodies. If,
years later, the virus enters the organism,
these antibodies will recognize and destroy
it.examples influenza virus vaccine,Polio vaccines
 A therapeutic vaccine is administered to a person
afflicted with a chronic viral infection, against which
naturally produced antibodies are ineffective. In other
words, therapeutic vaccines aim to increase the
activity of the body’s natural defenses. Examples
Bacillus Calmette-Guérin (BCG) vaccine,
Arcitumomab, Pankomab.

38. o An antigen is injected into a mouse, and after a
few weeks its spleen is removed and plasma
cells are extracted.
o The mouse's spleen cells are fused with
myeloms cells to create hybrid cells called
hybridoma cells. Each hybridoma cell
indefinitely produces identical antibody, and
the hybridoma cells are then screened using an
antigen/antibody assay that will reveal which
cells produce the desired antibody.
o The collection of selected hybridoma cells that
produce the preferred antibody are re-screened
multiple times until a pure line is isolated.
These cells are grown in a culture and/or
injected into into mice to induce tumors. The
cells can also be frozen and saved for later use.
Production of monoclonal antibodies

39. ACTION OF MONOCLONAL ANTIBODIES