The document summarizes key aspects of the adaptive immune system, including the roles of T lymphocytes and B lymphocytes. It discusses:
1) The two main types of lymphocytes are T lymphocytes and B lymphocytes. T lymphocytes mediate cell-mediated immunity while B lymphocytes mediate antibody-mediated or humoral immunity.
2) Helper T cells recognize antigens presented by antigen-presenting cells and activate other immune cells like B cells and cytotoxic T cells. Cytotoxic T cells directly kill infected cells.
3) B cells produce antibodies that target extracellular pathogens. Upon activation by helper T cells, B cells differentiate into plasma cells that secrete large amounts of antibodies, establishing antibody-mediated immunity.
3. Adaptive Immunity
• Immunity that an organism develops during
lifetime
• Develops after exposure to antigens
• Invovles the activity of lymphocytes
• Includes 3rd
line of defense
4. Adaptive Immunity (Specific immunity)
• Specificity
• Memory
• Ability to distinguish b/w self
vs non-self
• T and B cell
5. Types of Adaptive Immunity
1. Antibody-Mediated Immunity (AMI) or
Humoral Immunity
– B lymphocytes
2. Cell-Mediated Immunity (CMI) or Cellular
Immunity
– T lymphocytes
Note: B and T cells ……..blood, lymph, lymphoid
tissues such as spleen, lymph nodes etc.
7. CHECKPOINT
• 1. What are the two main types of
lymphocytes?
• 2. What is an antigen? Name some examples.
8. Cell-Mediated Immune Response
• T cells
• Immune resoponse to infected cells
( viruses, bacteria and parasites (Pathogens) within
cells)
• Defense against cancer and transplant cells
•Chapter 21, Immune System •8
9. T-Lymphocytes
• Helper T cells – secrete CYTOKINES
help B cells Tc cells to divide
• Cytotoxic T cells (killer T cells)
Kill infected body cells
• Memory T cells
remain in body
10. How do T cells know a cell is
infected?
• Infected cells digest some pathogens and MHC
proteins carry pieces to cell surface
• Antigen Presenting Cell (APC)
• Alerts Helper T cells
•MHC proteins displaying
foreign antigens
infected
cell
•T cell with
antigen receptors
•TH cell
11. •Chapter 21, Immune System •11
• MHC proteins,mark a cell as self
• The two classes of MHC proteins are:
– Class I MHC proteins – found on virtually all body cells
– Class II MHC proteins – found on certain cells in the
immune response
MHC Proteins
14. Helper T Cells (TH)
• bind to other white blood cells that have
previously encountered an antigen
– stimulate proliferation of other T cells
– Stimulate B cells that have already become bound
to antigen
• Without TH, there is no immune response
•Chapter 21, Immune System •14
15. The central role of Helper T Cells (Boss)
•Chapter 21, Immune System •15
•Figure 21.17a
16. Cytotoxic T Cell (Tc)
• Destroys infected body cells
– binds to target cell
– secretes perforin protein
• punctures cell membrane of infected cell
– apoptosis
•Chapter 21, Immune System •16
17. Cytotoxic T cells
•Killer T cell
binds to
infected cell
• Destroys infected body cells
– binds to target cell
– secretes perforin protein
• punctures cell membrane of infected cell
– apoptosis
•infected cell
•destroyed
19. •Cytotoxic T cell
•1 •2
•Accessory
protein
•Class I MHC
molecule
•Infected
cell
•Antigen
receptor
•Antigen
fragment
•Perforin
•Pore
•Gran-
zymes
20. The killing action of
cytoxic T cells on
an infected host
cell.
•Cytotoxic T cell
•3•1 •2
•Accessory
protein
•Class I MHC
molecule
•Infected
cell
•Antigen
receptor
•Antigen
fragment
•Perforin
•Pore
•Gran-
zymes
•Released
cytotoxic
T cell
•Dying
infected cell
22. • Human Immunodeficiency Virus
– virus infects and destroys helper T cells
• helper T cells don’t activate rest of immune system: killer T
cells & B cells
• AIDS: Acquired ImmunoDeficiency Syndrome
– infections by opportunistic
diseases
– death usually from
– “opportunistic” infections
• pneumonia, cancers
HIV & AIDS
•HIV infected T cell
23. ANTIBODY-MEDIATED (HUMORAL) IMMUNITY
• targets extracellular microorganisms (Bacteria
and viruses circulating in the blood)
• B-lymphocytes (B cells)………. Antibodies
• Antibodies… extracellular fluids and surface of B
cells
27. Antibody-mediated (humoral) immunity = AMI
• 1- Macrophages phagocytize
a pathogen and present an
antigen to a matching
helper-T cell
• 2- At the same time, some
pathogens contact B-cells
matching the pathogen’s
antigens
• The helper-T cells multiply,
secrete lymphokines which
stimulate the B-cells to
multiply and specialize into
plasma cells
• The plasma cells secretes
antibodies
28. The Nature of Antibodies
• Globular proteins called immunoglobulins
• Basic antibody structure has 4 polypeptide chains
– 2 identical light chains
– 2 identical heavy chains
• Regions of heavy and light chains
– Variable
– Constant
36. Types of Immunity
• Active Immunity
Natural active immunity - acquired due to infection
Artificial active immunity – vaccination
• Passive Immunity
Natural passive immunity
• placenta to the fetus
• Colostrum
Artificial passive immunity
• Injection of immune serum
Figure 43.17 The killing action of cytotoxic T cells on an infected host cell.
Figure 43.17 The killing action of cytotoxic T cells on an infected host cell.
Figure 43.17 The killing action of cytotoxic T cells on an infected host cell.
Figure 43.18 Activation of a B cell in the humoral immune response.
Figure 43.18 Activation of a B cell in the humoral immune response.
Figure 43.18 Activation of a B cell in the humoral immune response.
I. DEFINITION
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 field (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. 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
