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1. IMMUNITY
PRESENTED TO
MAM RABIA ASGHAR

2. The ability of human body to resist almost all kinds of
organisms and toxin that tend to damage the tissue and organs is
called immunity.
ANTIGEN
 Any invading agent like foreign proteins, organisms or toxins that
can produce an immune response is called an antigen
Antibody (Immunoglobulin)
 The specific globulin protein formed in the blood plasma as a
reaction to antigen is called antibody.
 Blood contains three types of globulins. alpha, beta and gamma.
 Antibodies are gamma globulins.
IMMUNIITY

3. TYPES OF IMMUNITY
There are two types of immunity
1. Innate Immunity
 It a natural, inborn and non-specific considered as first line of defense
without antigenic specificity.
 This is the natural resistance of the body to toxins, bacteria and other
foreign agents without any specific immune process.
 This immunity is present in both vertebrates and invertebrates.
 Impairment of innate immunity results in appearance of severe
infection.
2. Acquired Immunity
 Human body has ability to develop extremely powerful specific
immunity against invading agents and this is called acquired immunity.

4. The major components of innate immunity are:
 Humeral: Such as complements
 Cellular: Neutrophils, macrophages, eosinophils, mast cells and
natural killer cells
Principle mechanisms of innate immunity are as following:
Anatomical:
 Resistance of skin to invasion by organisms.
 Tight junctions in mucosa act as physical barrier and constant cell
turnover and desquamation deflect many invading organisms.
 Movement of bronchial cilia clears the bronchial tree.
INNATE
IMMUNITY

6.  Effector cells: Phagocytosis of bacteria and other invaders by
neutrophils, eosinophils. basophils, mast cells, monocytes. tissue
macrophages, and natural killer cell.
 Cell-derived Factors: Interferon's, tumor necrosis factor
 Destruction by the acid secretions off stomach and by the
digestive enzymes of organisms swallowed into stomach.
 Presence in the blood of certain chemical compounds that attach
to foreign organic or toxins and destroy them.
E.g. lysozyme, basic polypeptide, complement complex.
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7.  Specific immune responses are generated by two specific cell
populations bearing clonally distributed receptors, these cells are
B-lymphocytes and T-lymphocytes.
 Activation of B-lymphocytes results in synthesis and secretion of
immunoglobulin (antibody) of the same specificity. T-Iymphocytes
also express a surface antigen receptor with clonal specificity
• Humoral (Antibody-mediated) immunity
 In this type of immunity body develops circulating antibodies from
B-lymphocytes, which are globulm molecules and are capable of
attacking the invading agents.
 1-tumoral immunity is effective against extracellular bacteria
(majority of bacteria is extracellular) while its role against
intracellular bacteria, viruses, fungi and parasites is limited.
ACQUIRED IMMUNITY

8. • Cell-mediated immunity
 In this type of immunity body develops large number of
T- lymphocytes which are specifically activated against foreign
agent. These activated or sensitized lymphocytes have the ability
to attach a foreign agent and to destroy it. Cellular immunity is
required against viral, fungal. parasitic infections and infections
with intracellular bacteria such as mycobacterium tuberculosis an
mycobacterium leprae.
CONTINUED…

10. There are two types of immune responses primary and secondary.
 Memory is an essential component of immune response because it
facilitates enhanced, more effective response on second and
subsequent exposure to a particular antigen.
 Based on whether the immune system has been previously exposed
to the antigen or not, two types of immune response can be
recognized: Primary and secondary.
TYPES OF IMMUNE RESPONSE
1. Primary immune response
 The primary immune response follows the first exposure to a
particular antigen.
 Although antigen is recognized as soon as it is introduced into the
body, several days elapse before enough immunoglobulin (antibody) is
produced to be detected as an increase in serum immunoglobulin
levels.

11. 2. Secondary immune response
 The e secondary immune response follow's repeat exposure to an antigen.
 Recognition again occurs immediately, but production of detectable
increase in serum immunoglobulin occurs snatch more rapidly than in
primary response.
 This response is much more forceful.
 This ability of specific secondary response is a function of immunologic
memory.
Primary Secondary
Slow in onset Rapid in onset
Low in magnitude High in magnitude
Short lived Long lived
IgM (IgG in later stages IgG (or IgA, or igE
 IgM is the first immunoglobulin produced during the primary
response, IgG production follows (it comes later).
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13.  An understanding of the two types of immune response is helpful in the
serologic diagnosis of infectious disease.
 Early in the course of infection, serologic tests for specific immunoglobulin
will be negative.
 After the first week of primary immune response, IgM antibodies become
detectable in serum, and levels increase rapidly but decline also rapidly.
 IgG appears later (increased specific IgM indicates active or recent
disease). Rising level of specific IgM and then IgG 4-fold is diagnostic of
active infection (less than 4-fold rise may occur as a nonspecific immune
response).
 IgG levels remain high for a long period after infection, so that elevated
level of only IgG may signify only past-infection and not necessarily recent
or active disease.
Clinical Uses of Immune System
(Serologic diagnosis of infection)

14.  Immunization represents the practical use of immunologic
memory to provide protection against infectious disease. Two
major methods are available:
IMMUNIZATION
1. Passive immunization
 Passive immunization is achieved by administration of antibody
to an individual exposed to infection.
 These antibodies may he collected from human serum (such as
antibodies against hepatitis A) or animal serum (such as
antibodies against tetanus).
 This type of immunization is for short period.

15. 2. Active immunization
 Active immunization provides immunological protection prior to
infection by stimulating m mine system in advance.
 The administration of antigens of the infectious agent (either killed
organisms attenuated live organism or inactive toxins) to stimulate the
host's immune response to produce high antibody levels and memory
cells provides excellent long-term protection
 For example the childhood vaccines for polio, measles, mumps,
rubella and hepatitis B.
 The protection induced by vaccine is lifelong.
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16. Antigen
 Any invading agent like foreign proteins, organisms or toxins that can
produce an immune response is called an antigen.
Antibody (immunoglobulin)
 The specific globulin protein formed in the blood plasma as a reaction to
antigen is called immunoglobulin or antibody.
 Blood contains three types of globulin, alpha, beta and gamma.
Antibodies are gamma globulins.
 Immunoglobulins are synthesized by plasma cells that differentiate from
transformed, antigen stimulated B-lymphocytes. IgM and IgG activate
complement system that is associated with acute inflammatory reaction.
ANTIGENS AND ANTIBODIES

17.  Immunoglobulins are found in serum and in secretions from
mucosal surfaces.
 There are five classes of immunoglobulins IgM, IgG, IgA,IgD and IgE
 They are produced and secreted by plasma cells which are found
mainly within lymph nodes, and which do not circulate.
 Plasma cells are derived from B lymphocytes
 Each antibody is composed of two light and two heavy chains. Each
chain has a constant and variable portion.
• Variable portion: It attaches specifically to a particular type of
antigen.
• Constant portion: It has receptor for attachment of complement
complex.
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19.  IgG
1. It is most abundant type of immunoglobulin present in serum.
2. Although it appears in late phase of primary response, it is the main
antibody in secondary response (while IgM in primary response).
3. It provides an important detersive against bacteria and viruses.
4. It is the only antibody that can cross placenta (due to relatively low
molecular weight)
5. It is the most important immunoglobin in newborn
6. It as opsin and therefore enates plagiotropic.
7. It also activates complement system.
TYPES OF IMMUNOGLOBULINS
 IgD
Its role is undetermined.

20.  IgM
2. It provides defense against bacteria and viruses.
3. It can not cross placenta.
4. It also activates complement system.
5. It is the main immunoglobulin produced early in the primary response.
 IgE
1. It mediates type I hypersensitivity reaction by causing release of mediators
from mast cells and basophils upon exposure to antigen.
2. It is the main host defense against helininth (worm) infections such as
ascaris, hook worm.
3. It can not cross placenta and does not activate complement.
4. Its concentration in serum is very low but rises in allergy and helminth
infections.

21.  IgA
 IgA made by mucosal plasma cells is secreted in proximity to the
lining epithelial cells.
 It plays a critical role in the defense of mucous membranes such
as respiratory mucosa against microbial pathogens and other
antigens.
 It is present in mucosal epithelium and mucosal secretions, thus
provides mucosal protection (therefore IgA is also called
secretory antibody).
 The mucosal immune system provides the initial immunological
barrier against most pathogens, in particular, immunoglobulin A
(IgA), the predominant mucosal antibody, is thought to mediate
defense functions at different anatomic levels in relation to
mucosal epithelium

22.  Acquired immunity is the product of body's lymphoid tissue.
There are two types of lymphoid tissue.
A. Central lymphoid tissue such as:
• Thymus
• Bone marrow
B. Peripheral lymphoid tissue such as:
• Lymph nodes
• Spleen
• Tonsils
• Gut associated lymphoid tissue
• Peripheral blood
 These are the tissues in which mature lymph reside and respond to
antigenic stimuli.
LYMPHOID TISSUE

23.  Lymphocytes
Lymphocytes are the cells derived from lymphoid stem cells in the
bone marrow and develop in the fetal life.
Lymphocytes may be classified on the basis of their site of
development in the feus.
 T lymphocyte
Develop in thymus of the fetus
 B Lymphocytes
Develop in fetal liver or bone marrow (in bursa of fabricius in birds)
CELLS OF THE IMMUNE SYSTEM

24.  T-lymphocytes
 They arise from the stem in the bone marrow.
 They are immature and are taken to the thymus for maturation during
fetal life.
 Mature T-lymphocytes circulate in the blood and pass to peripheral
lymphoid tissue e.g. paracortex of lymph nodes, periarterial lymphoid
sheath in the white pulp of spleen.
 T lymphocytes continuously and actively recalculate between the
peripheral blood and peripheral lymphoid tissue.
 About 80 to 90% of peripheral blood lymphocytes are T-lymphocytes.

25.  Following stimulation (activation) by specific antigen.
 T-lymphocytes transform into large actively dividing cells known as
transformed T-lymphocytes, which then divide to produce
effectors cells.
 These effectors T-lymphocytes are also called sensitized, cytotoxic
or killer T cells.
 There are certain antigens on T lymphocytes, dividing the
lymphocytes, in C subsets like CD4 are helper T cells while CD8 are
suppressor T cells.
CONTINUED…

26.  Cellular immune reaction: They are responsible for cell-mediated
immunity e.g. against foreign histocompatibility antigens, virus
infected cells, and some tumor cells. T cells either directly kill the
recognized cell or produce cytokines (lymphokines) such as
interleukins, interferon, tumor necrosis factors) that regulate the
functions of macrophages or other lymphocytes.
 Regulatory function: They control the T and B cell mediated response
through:
• T-helper cells which help in the production of T and B cells.
• T-suppressor cells which suppress T and B cell function.
Functions of T-Iymphocytes

27.  B-Iymphocytes:
 They also arise from the stem cells in the bone-marrow and are
taken to some known area of body, possibly the fetal liver, bone
marrow GIT mucosa (bursa of fabricius in birds) for maturation.
 Mature B-lymphocytes are taken to peripheral lymphoid tissue e.g.
lymph node, spleen.
 About 10- 20% of peripheral blood lymphocytes are B cells.
 Functions of B-Lymphocytes
 After stimulation by an antigen 'B cells differentiate into plasma
cells that secrete immunoglobins (antibodies). B-lymphocyte
lymphoblast plasmoblast plasma cells antibodies.

28.  Macrophages
 The macrophages are the large, mononuclear highly phagocyte cells,
occurring in the walls of blood vessels (adventitial cells) and in loose
connective tissue (histolytic).
 They are usually fixed but when stimulated by inflammation, they
become mobile.
 Functions of macrophages
 They present antigen to immunocompetent T cells.
 They produce interleukin-1 which promotes the differentiation of both T
and B lymphocytes.
 They lyse tumor cells by secreting toxic metabolites and proteolytic
enzymes.

30.  Natural killer cells
 The Natural Killer (NK) cells are large granular lymphocytes which are
capable of lysing a variety of tumor cells, virus-infected cells, and
fungi.
 They differ from T and B lymphocyte in respect that they do not
require prior sensitization for expression of their function, which is
essential for T and B cell function.
 NK cells are considered to provide the first line of defense against
tumors and virus infections.

32. Effects of immune deficiency
Infections:
 T-lymphocytes deficiency predisposes to infections with viruses,
mycobacteria, fungi, pneumocystis carni and toxoplasma Gondi
infection
 B-lymphocyte deficiency predisposes to pyogenic bacterial
infections.
Malignancies:
 Kaposi’s sarcoma
 B cell lymphoma
Auto immune diseases
Graft versus host diseases