humoral cell mediated immunity, antigen hapten antibodies

Date:6/23/2021 www. qadricohs.edu.pk FB Page: Qadri College of Health Sciences, Karachi, Sindh, Pakistan. 1
QADRI COLLEGE OF HEALTH SCIENCES, KARACHI
U-3, 4 OF
“DEFENSE MECHANISMS OF THE BODY”
By: Aftab H. Abbasi
RN, DCHN, BSN, MA, LL.B
Lecturer Nursing
Qadri College of Health Sciences Karachi

“DEFENSE MECHANISM OF THE BODY”
- This unit focuses on the resistance of the
body which microorganism’s encounter
where they enter in the human body.
- This unit highlights the importance of the
resistance or defense of the body which
will help learners in understanding that
why infection occurs sometimes and not
always.

At the completion of this unit learners will
be able to:
1- Explain the role of good health in protection against the microbial
infection.
2- Define Resistance and Susceptibility.
3- Define Nonspecific Resistance.
4- Describe the role of the skin and mucous membrane in nonspecific
Resistance.
5- Explain the process of Phagocytosis.
6- Define the Specific Resistance, Innate Resistance and Immunity.
7- Explain four types of acquired Immunity.

At the completion of this unit learners will be
able to:
8- Differentiate between humoral and cell mediated immunity.
9- Define Antigens, hapten and antibodies.
10- List the five classes of antibodies and their functions.
11- Explain the role of memory, tolerance and specificity in immunity.
12- Distinguish between primary and secondary immune response.
13- Define Hypersensitivity.
14- Differentiate between i.e. delayed and immediate Hypersensitivity.

8- Humoral / Cell mediated immunity.
Def: Humoral immunity:
or humoural immunity is the aspect
of immunity that is mediated (to settle, disputes, strikes, etc. as an
intermediary between parties; reconcile.) by macromolecules found in
extracellular fluids such as secreted
antibodies, complement proteins, and
certain antimicrobial peptides.
Humoral immunity is named so because it
involves substances found in the humors,
or body fluids.

Def: Cell-mediated immunity:
is an immune response that does not
involve antibodies. Rather, cell-mediated
immunity is the activation of phagocytes,
antigen-specific cytotoxic T-lymphocytes,
and the release of various cytokines
in response to an antigen.

Here are some differences:
S.N. Characteristics Humoral Immunity Cell-mediated Immunity
1. Definition The immunity mediated
by macromolecules found
in the extracellular body
fluids is called humoral
immunity. (“humor” a
medieval term for body
fluid)
The immunity that identifies
and destroys infected cells
in the body is called cell-
mediated immunity.
2. Mediator The main cell involved in
humoral immunity are B-
cells.
The main cell involved in
cell-mediated immunity are
T-cells.
3. Components B cells, T cells, and
macrophages.
Helper T cells, cytotoxic T-
cells, natural killer cells,
and macrophages.

4. Pathogen The humoral immunity
protects against
extracellular pathogens
and also their toxin.
The cell-mediated
immunity protects against
intracellular pathogens.
5. Pathogen
recognition
Recognize antigens or
pathogens that are
circulating in the lymph
or blood.
It responds to any cell that
displays aberrant MHC
markers, including cells
invaded by pathogens,
tumor cells, or transplanted
cells.
6. Antigen
detectors
Phagocytes and
antibodies themselves
are used to detect
antigens.
Receptors and MHC
molecules on the cell
surfaces are used to detect
antigens.
7. Antigen Binding B-cells produce
antibodies and the
antibodies bind to
antigens.
T-cell receptors on cells
bind to T-cells which in turn
bind to antigens.

8. Antigen
Processing
Do not require the
processing of antigens.
Antigens must be
processed and presented
for T-lymphocyte mediated
response.
9. Receptor
Involved
It involves B-cell receptors
(BCRs).
It involves T-cell receptors
(TCRs).
10 Accessory
surface
receptors/mole
cules
Igα, Igβ, Fc receptors,
CD40, CD21
CD3 molecular complex
Dimer of ∑ chain, CD4,
CD8, CD2, CD28,
integrins
11 Type of T-cell
involved
Only the T helper cell
(CD4+) is involved.
Both CD4+ and CD8+ T
cells are involved.
12 Antibodies
formation
Antibodies are formed in a
humoral response.
Antibodies are not formed
in a cell-mediated immune
response.

13 Onset The onset is rapid. The onset is delayed.
14 Result The end result of the
activation is the
differentiation of plasma
B-cells, secreting
antibodies.
The end result of the
activation is the secretion
of cytokines.
15 Protection
against
Extracellular bacterial or
viral pathogens.
It protects against fungus,
viruses, and intracellular
bacterial pathogens.
16 Immunological
surveillance
It does not provide
immunological
surveillance.
It provides immunological
surveillance.
17 Hypersensitivity
reactions
Hypersensitivity type I,
II, and III is mediated by
humoral immunity.
Hypersensitivity type IV is
mediated by cell-mediated
immunity.

18 Role in Organ
transplantation
and Grafting
It may be involved in
early graft rejection due
to preformed antibodies.
It participates in rejections
of organ transplants.
19 Immunity
against cancer
It does not provide
immunity against cancer.
As it destroys the tumor
and cancerous cells, it
provides protection
against cancer.
20
Assessment
method
From plasma level of
antibodies
Skin test for the
development of delayed-
type of hypersensitivity
References:
https://microbenotes.com/differences-between-humoral-immunity-and-cell-mediated-immunity/
2- http://www.differencebetween.net/science/difference-between-humoral-and-cell-mediated-immunity/
3- http://www.easybiologyclass.com/difference-between-cell-mediated-and-humoral-immunity-comparison-table/
4-https://www.researchgate.net/publication/320180727_Difference_Between_Humoral_and_Cell_Mediated_Immunity
5- http://howmed.net/pathology/comparison-of-humoral-and-cell-mediated-immunity/
6- https://medicscenter.com/humoral-vs-cell-mediated-immunity/

9- Antigens, Haptens and antibodies.
Antigen Definition:
Antigens are molecules or molecular structures that
are foreign to the body and generally induce an
immune reaction in the form of the production of
antibodies against them.
- In simple words, antigens can be anything that
doesn’t belong to the body and are foreign.
- Even though antigens are usually defined by the
induction of an immune response, all antigens
might not induce an immune response. The
antigens that induce a response are termed
immunogens.

Antigens/ Haptens
- Antigens are indicated by the term ‘Ag’, and these can occur
in different forms like pollen, viruses, chemicals, or bacteria.
- The concept of antigen arose from the fact that our body
can distinguish between the components of the body and
foreign particles.
- In response to these antigens, the body induces the
production of antibodies that act against the said antigens.
- Most antigens in humans are proteins, peptides, or
polysaccharides; however, lipid and nucleic acids can also
act as antigens when combined with proteins or
polysaccharides.
- In addition, antigens might also be intentionally introduced
into the body in the form of vaccines in order to induce the
adaptive immune system of the body against the antigen.

Classification of Antigens
1. Types of antigen-based on their origin:
Antigens can be classified into two groups on the basis of
their origin:
a. Exogenous Antigens:
- Exogenous antigens are the antigens that are
originated outside the body of the host and, thus, are
foreign to the host.
- These antigens might enter the body through
inhalation, ingestion, or injection and then circulate
throughout the body via bodily fluids.
b. Endogenous Antigens:
- Endogenous antigens are antigens that originate
within the body of the host during metabolism or as a
result of intracellular viral or bacterial infection.

- Endogenous antigens are usually the
cells of the body or fragments,
compounds, or antigenic products of
metabolism.
- Endogenous antigens might result in
autoimmune diseases as the host
immune system detects its own cells and
particles as immunogenic.

2. Types of antigens on the basis of
immune response:
Antigens can be classified into two distinct groups on the basis
of immune response:
a. Complete antigens/ Immunogens:
- Complete antigens or Immunogens are
antigens that elicit a specific immune
response.
- These antigens can induce an immune
response by themselves without any carrier
particles.
- These are usually proteins, peptides, or
polysaccharides with high molecular weight
(greater than 10,000 Da).

b. Incomplete antigens/ Haptens:
- Incomplete antigens or haptens are antigens
that cannot generate an immune response
by themselves.
- These are usually non-protein substances
that require a carrier molecule to form a
complete antigen.
- Haptens have a low molecular weight
(usually less than 10,000 Da) and fewer
antigenic determinant sites.
- The carrier molecule bonded to the hapten is
considered a non-antigenic component and
is a protein or a polysaccharide molecule.

Antibodies
Antibody Definition:
Antibodies, also known as
immunoglobulins, are proteins produced
by lymphocytes as a result of interaction
with antigens. Antibodies are a part of the
humoral immune of the adaptive immune
system where each antibody identifies a
specific antigen and protects the body
against it.
- Antibodies are glycoproteins that bind to
antigens with a high degree of specificity
and affinity.

Antibodies
- B lymphocytes are stimulated by the binding
of antigen, which results in the secretion of
millions of antibodies in the bloodstream.
- The produced antibodies circulate through
the bloodstream and neutralize antigens that
are identical to those that triggered the
immune response.
- The binding of antibodies to microorganisms
or other such antigens can result in the
microorganism being immobile or preventing
them from penetrating the cells.

Antibodies
- Antibodies carry out two principal functions in the
immune system. The first function is the
recognition and binding to foreign bodies. The
second more important function is to trigger the
elimination of the attached foreign material.
- Since millions of antibodies are produced during
an immune response, some of these remain in
circulation in the blood for several months. This
provides an extended immunity against the
particular antigen.
- Each antibody is a Y-shaped protein where each
tip of the Y contains a paratope that recognizes
an epitope of a particular antigen.

Antibodies
- Antibodies can be classified into different
classes based on different structures and
functions. References: https://microbenotes.com

By: Aftab H. Abbasi
RN, DCHN, BSN, MA, LL.B
Lecturer Nursing
Qadri College of Health Sciences Karachi

humoral cell mediated immunity, antigen hapten antibodies

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