4. ā Body defense mechanisms & its characteristics
ā Adaptive immunity & Its responses to antigens
ā Cells of Adaptive Immune Response
ā Organs of Immune Responses
ā Types of Adaptive immunity
ā Role of Antigens receptors & Cytokines in Immune
Response
ā T-Dependent Vs T-Independent Antigens
Over view of Presentation
7. Characteristics of Adaptive Immunity
ā¢Recognition of self versus non-
self
ā¢Response is specific
ā¢Retains a āmemoryā allowing an
accelerated second response
ā¢Can respond to many different
materials
9. ā The adaptive or specific immune response involves two
main lines of defence: humoral immunity and cell
mediated immunity.
ā Humoral immunity involves Blymphocytes (Bcells)
ā Cell-mediated immunity involves T lymphocytes (T cells)
ā Both B cells and T cells are derived from stem cells in the
bone marrow, however they mature in different parts of the
body.
ā Bcells mature in the bone marrow then travel to lymphatic
tissues, especially the spleen and lymph nodes
ā T cells mature in the thymus
Humoral and cell-mediated immunity
11. Immune System Response to Antigens
Humoral Immunity
ā¢Involves antibodies (secreted from
B cells) dissolved in the blood
plasma.
ā¢Demonstrated as an immune
response using only the blood
serum(Plasma without clotting protiens).
ā¢Defense against bacteria, bacterial
12. Cell-Mediated Immunity
ā¢Involves the activities of specific white
blood cells (T cells).
ā¢Defense against cancer cells, virus-
infected cells, fungi, animal parasites, &
foreign cells from transplants.
Immune System Response to Antigens
(cont.)
13.
14. Cells involved in specific immune mechanisms are:
I) Hematopoitic leucocytes(derived from mesoderm)
1- Lymphoid
* T-lymphocytes:
- Antigen specific cells carrying CD3 complex, CD4, CD8
- Dominant blood lymphocytes (70%)
- Produce cytokines
- Activation of other cells (Th CD4)
- Suppressors for others (Ts CD8)
Cells Of Immune Response
15. * B-lymphocytes:
- Antigen specific cells with surface receptor
- Less common lymphocytes (20%)
- Responsible for antibody production
* NK, K cells:
- Not antigen specific
- Carry Fc receptors , NK-target cell receptor
Cells Of Immune Response (cont.)
16. 2- Monocytic myeloid
a- Monocyte-tissue macrophages:
. Non specific
. Carry Fc receptors
. Phagocytic
. Antigen processing and presenting cells
. Produce cytokines
b- Neutrophils:
. Non specific
. Carrying Fc, complement molecules
Cells of Immune Response (cont.)
16
17. Cells of Immune Response (cont.)
c- Eosinophil:
. Non specific
. Carrying Fc receptor
. Produce allergic mediators
d- Basophils and Mast cells:
. Non specific
. Carrying Fc receptors
. Produce allergic mediators17
18. ŠŠ-Non hematopoietic cells:
- Dendritic cells
- Astrocytes and
- Endothelial cells
Function : antigen presentation
Cells of Immune Response (cont.)
19. Cells of the immune systemBone graft
Multipotential
stem cell
Hematopoietic
stem cell
Platelets
Macrophage
Erythrocytes
Eosinophil
Neutrophil
Megakaryocyte
Mast cell
Basophil
T lymphocyte
Natural killer cell
Dendritic cell
B lymphocyte
Lymphoid progenitor cell
Myeloid
progenitor
cell
Monocyte
Marrow
Bone
19
20. Tonsils and
adenoids
Lymph
nodes
Appendix
Lymphatic
vessels
Lymph nodes
Thymus
Peyerās
patches
Spleen
Lymphatic
vessels
Lymph nodes
Organs of the Immune Response
ā¢ The organs of our immune system
are positioned throughout our body.
ā¢ They are called lymphoid organs
because they are home to
lymphocytes--the white blood cells
that are key operatives of the
immune system. Within these
organs, the lymphocytes grow,
develop, and are deployed.
ā¢ Key organs include the bone
marrow, the thymus and the spleen.
ā¢ In addition to these organs, clumps
of lymphoid tissue are found in
many parts of the body, especially
in the linings of the digestive tract
and the airways and lungs--
gateways to the body. These
tissues include the tonsils, adenoids
Bone
marrow
21. ā The production of antibodies against a
specific disease by the immune system.
ā Naturally acquired through disease
ā Artificially acquired through vaccination
ā Vaccines include inactivated toxins, killed
microbes, parts of microbes, and viable but
weakened microbes.
ā Active immunity is usually permanent
Active Immunity
22. ā A vaccinated person has a secondary
response based on memory cells when
encountering the specific pathogen.
ā Routine immunization against infectious diseases
such as measles and whooping cough, and has
led to the eradication of smallpox, a viral disease.
ā Unfortunately, not all infectious agents are easily
managed by vaccination.
Active Immunity
(cont.)
23. āPassive Immunity- Protection
against disease through antibodies
produced by another human being or
animal.
āEffective, but temporary
āMaternal antibodies (IgG)
āColostrum (IgA)
Passive Immunity
24. āPassive immunity can be transferred
artificially by injecting antibodies from
an animal that is already immune to a
disease into another animal.
ā Rabies treatment: injection with antibodies
against rabies virus that are both passive
immunizations (the immediate fight) and
active immunizations (longer term
Passive Immunity (Cont.)
25. B Cells
ā¢Mature in bone marrow
ā¢Involved in humoral immunity
ā¢Once activated by antigen, proliferate
into two clones of cells: plasma cells
that secrete antibodies and memory
cells that may be converted into
plasma cells at a later time
28. ā Antibodies constitute a group of globular
proteins called immunoglobins (Igs).
ā A typical antibody molecule has two identical
antigen-binding sites specific for the epitope
that provokes its production.
Antibodies
30. Immunoglobin Classes
IgM
ā¢ 1st response to antigen
ā¢ Canāt cross placenta
ā¢Involved in agglutination and
complement activation
IgG
ā¢ Most common form
ā¢ Crosses blood vessels
ā¢ Crosses placenta (passive
immunity to fetus)
ā¢Involved in agglutination and
complement activation
IgA
ā¢ Secreted from mucus membranes
ā¢ Prevents attachment of bacteria to
epithelial surface
ā¢ In colostrum
ā¢ Important in mucosal immunity
IgD
ā¢ B cell activation
ā¢ Canāt cross placenta
ā¢Important in development
of the immune response
IgE
ā¢ Histamine reactions
and allergies
ā¢Attaches to mast cells
31. Mechanisms on Antibody Action
cipitation of soluble antigens
glutination of foreign cells
utralization
hanced phagocytosis
mplement activation leading to cell lysis
mulates inflammation
32. ā The binding of antibodies to antigens to form
antigen-antibody complexes is the basis of
several antigen disposal mechanisms.
32
34. T Cells
ā¢Mature in thymus
ā¢Involved in cell-mediated immunity
ā¢Activated when another cell
presents antigen to them
ā¢Several types of T cells: cytotoxic T
cells, helper T cells, suppressor
T cells, and memory T cells
35. ā¢ There are two main types of T cells, and
each responds to one class of MHC
molecule.
ā Cytotoxic T cells (TC) have antigen receptors
that bind to protein fragments displayed by the
bodyās class I MHC molecules.
ā HelperT cells (TH) have receptors that bind to
peptides displayed by the bodyās class II MHC
molecules.
T Cells
37. Role of antigen receptors in the
immune response
ā¢ Both B cells and T cells carry customized receptor
molecules that allow them to recognize and respond to
their specific targets.
ā¢ The Bcellās antigen-specific receptorthat sits on its
outersurface is also a sample of the antibody it is
prepared to manufacture; this antibody-receptor
recognizes antigen in its natural state.
ā¢ The T cellās receptor systems are more complex. T cells
can recognize an antigen only afterthe antigen is
processed and presented in combination with a special
type of majorhistocompatibility complex (MHC)
marker.
ā¢ Killer T cells only recognize antigens in the grasp of
Class I MHC markers, while helper T cells only
38. Antigen receptors
Killer cell
Infected cellAntigen-presenting cell Antigen-presenting cell
CD8
protein
Cell
membrane MHC
Class I
MHC
Class I
Antigenic
peptide
T cell
receptorCD4
protein
Cell
membrane MHC
Class II
Antigenic
peptide
T cell
receptor
Cell
membrane
Antigen
Antigen-
specific
receptor
B cell
Killer cell
Infected cellAntigen-presenting cell Antigen-presenting cell
CD8
protein
Cell
membrane MHC
Class I
MHC
Class I
Antigenic
peptide
T cell
receptorCD4
protein
Cell
membrane MHC
Class II
Antigenic
peptide
T cell
receptor
Cell
membrane
Antigen
Antigen-
specific
receptor
Helper T cellB cell
39. Role of cytokines in immune response
ā¢ Cytokines are diverse and potent chemical messengers secreted by
the cells of immune system. They are the chief communication
signals of our T cells. Cytokines include interleukins, growth factors,
and interferon.
ā¢ Lymphocytes, including both T cells and B cells, secrete cytokines
called lymphokines, while the cytokines of monocytes and
macrophages are dubbed monokines. Many of these cytokines are
also known as interleukins because they serve as a messenger
between white cells, or leukocytes.
ā¢ Interferon are naturally occurring cytokines that may boost the
immune systemās ability to recognize cancer as a foreign invader.
ā¢ Binding to specific receptors on target cells, cytokines recruit many
other cells and substances to the field of action. Cytokines
encourage cell growth, promote cell activation, direct cellular traffic,
and destroy target cells--including cancer cells.
ā¢ When cytokines attract specific cell types to an area, they are called
chemokines. These are released at the site of injury or infection and
40.
41. āT-independent antigens
āT cells activated by binding to certain
antigens
āNo memory cells generated
āWeaker response than t-dependent
āT-dependent antigens
āMost antigens require co-stimulation to
evoke a B-cell response
āAntibody production stimulated with
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Cells destined to become immune cells, like all blood cells, arise in your bodyās bone marrow from stem cells. Some develop into myeloid progenitor cells while others become lymphoid progenitor cells.
The myeloid progenitors develop into the cells that respond early and nonspecifically to infection. Neutrophils engulf bacteria upon contact and send out warning signals. Monocytes turn into macrophages in body tissues and gobble up foreign invaders. Granule-containing cells such as eosinophils attack parasites, while basophils release granules containing histamine and other allergy-related molecules.
Lymphoid precursors develop into the small white blood cells called lymphocytes. Lymphocytes respond later in infection. They mount a more specifically tailored attack after antigen-presenting cells such as dendritic cells (or macrophages) display their catch in the form of antigen fragments. The B cell turns into a plasma cell that produces and releases into the bloodstream thousands of specific antibodies. The T cells coordinate the entire immune response and eliminate the viruses hiding in infected cells.
<number>
The organs of your immune system are positioned throughout your body.
They are called lymphoid organs because they are home to lymphocytes--the white blood cells that are key operatives of the immune system. Within these organs, the lymphocytes grow, develop, and are deployed.
Bone marrow, the soft tissue in the hollow center of bones, is the ultimate source of all blood cells, including the immune cells.
The thymus is an organ that lies behind the breastbone; lymphocytes known as T lymphocytes, or just T cells, mature there.
The spleen is a flattened organ at the upper left of the abdomen. Like the lymph nodes, the spleen contains specialized compartments where immune cells gather and confront antigens.
In addition to these organs, clumps of lymphoid tissue are found in many parts of the body, especially in the linings of the digestive tract and the airways and lungs--gateways to the body. These tissues include the tonsils, adenoids, and appendix.
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I. DEFINITIONĀ
Immunoglobulins (Ig) Glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies. The immunoglobulins derive their name from the finding that they migrate with globular proteins when antibody-containing serum is placed in an electrical fieldĀ (Figure 1).
II. GENERAL FUNCTIONS OF IMMUNOGLOBULINS
A. Antigen binding Immunoglobulins bind specifically to one or a few closely related antigens. Each immunoglobulin actually binds to a specific antigenic determinant. Antigen binding by antibodies is the primary function of antibodies and can result in protection of the host.Ā The valency of antibody refers to the number of antigenic determinants that an individual antibody molecule can bind. The valency of all antibodies is at least two and in some instances more.
B. Effector Functions Frequently the binding of an antibody to an antigen has no direct biological effect. Rather, the significant biological effects are a consequence of secondary "effector functions" of antibodies. The immunoglobulins mediate a variety of these effector functions. Usually the ability to carry out a particular effector function requires that the antibody bind to its antigen. Not every immunoglobulin will mediate all effector functions. Such effector functions include:
1. Fixation of complement - This results in lysis of cells and release of biologically active molecules (see chapter two)
2. Binding to various cell types - Phagocytic cells, lymphocytes, platelets, mast cells, and basophils have receptors that bind immunoglobulins. This binding can activate the cells to perform some function. Some immunoglobulins also bind to receptors on placental trophoblasts, which results in transfer of the immunoglobulin across the placenta. As a result, the transferred maternal antibodies provide immunity to the fetus and newborn
Immunoglobulin classes
IgM
First response to antigen
IgG
Most common form
IgA
Secreted form
IgD
B cell activation
IgE
Histamine reactions and allergies
<number>
<number>
Both B cells and T cells carry customized receptor molecules that allow them to recognize and respond to their specific targets.
The B cellās antigen-specific receptor that sits on its outer surface is also a sample of the antibody it is prepared to manufacture; this antibody-receptor recognizes antigen in its natural state.
The T cellās receptor systems are more complex. T cells can recognize an antigen only after the antigen is processed and presented in combination with a special type of major histocompatibility complex (MHC) marker. Killer T cells only recognize antigens in the grasp of Class I MHC markers, while helper T cells only recognize antigens in the grasp of Class II MHC markers. This complicated arrangement assures that T cells act only on precise targets and at close range.
