ch 17 - adaptive immunity f 2017 - napa valley college · the result of helper t cell activation is...
TRANSCRIPT
11/24/2017
1
Adaptive Immunity
Chapter 17
BIO 220
Adaptive Immunity
• Adaptive defenses acquired through infection or vaccination
• Specificity for particular pathogen
• Memory for most previously encountered antigens
• Ability to distinguish “self” from “not self”
B and T lymphocytes
Fig. 17.1
Immunocompetence
• This is the ability to carry out adaptive immune responses
• Selective process
• In an immunocompetent lymphocyte, specific proteins are inserted into the plasma membrane of that cell
• Antigen receptors (B & T)
• CD4 (T)
• CD8 (T)
11/24/2017
2
Role of cytokines in adaptive immunity
• Cytokines are chemical messengers composed
of proteins or glycoproteins
– Interleukins (communication between leukocytes)
– Chemokines (movement of leukocytes to areas of
injury or infection)
– Interferons
– Tumor necrosis factor (inflammatory reactions)
– Hematopoietic cytokines (controls formation of
formed elements from stem cells)
Antigens
• Substances that cause the production of antibodies
• Microbial antigens are typically proteins or large polysaccharides that are components of microbe capsules, cell walls, flagella, fimbriae, toxins, viral coats, or other microbial surfaces
• Complete antigens can induce an immune response leading to production of antibodies, which can then bind the antigen
• Usually antibodies recognize and interact with specific regions on antigens called epitopes(antigenic determinants)
Epitopes
Fig. 17.2
Remember PAMPs?
Haptens
• These are incomplete antigens
• Foreign substance with a low molecular weight (< 10,000) is not antigenic unless it is attached to a carrier molecule
• Once an antibody has been formed against a hapten, the antibody will react with the hapten regardless of whether or not the carrier protein is present
• i.e. Penicillin
11/24/2017
3
Hapten Example: Chemical in Poison Ivy
Antigen-Presenting Cells (APCs)
• B cells
• Dendritic cells
• Macrophages
Figs. 17.10, 17.11
Types of Adaptive Immunity
Cell-Mediated
• T cells
• Effective against
– Intracellular pathogens
like bacteria, viruses, or
fungi
– Cancer cells
– Foreign tissue implants
Antibody-Mediated
(Humoral)
• B & T cells
• Antibody production
• Effective against
– Extracellular pathogens
(mostly bacteria,
bacterial toxins, viruses)
11/24/2017
4
Cell-Mediated Immunity
Players in cell-mediated immunity
• Antigen-presenting cells
– Macrophages & dendritic cells
• Helper T cells
– TH1
• Cytotoxic T cells
• Infected body cells
• Pathogens entering the
GI tract are transported
through M cells to
Peyer’s patches.
• Within Peyer’s patches
the antigens will be
exposed to APCs and
lymphocytes.
Fig. 17.9
11/24/2017
5
APCs at work
Fig. 17.12 Fig. 17.13
The result of helper T
cell activation is clonal
expansion.
Activation of cytotoxic T cells
Fig. 17.14
11/24/2017
6
22_17 Apoptosis
Fig. 17.15
Fig. 17.20
Natural killer cells (NKCs)
• Can also destroy certain virus – infected cells
and tumor cells
– If MHC Type I molecules are missing on cell, NKCs
destroy cell
• Can also attack parasites
11/24/2017
7
Antibody - dependent
cell - mediated toxicity
• Large pathogens like
protozoa or helminthes
are coated with
antibodies
• Eosinophils, macrophages,
NK cells bind to antibodies
• Ultimately target cells are
lysed
Fig. 17.16
Antibody-Mediated Immunity
Players in Antibody-mediated immunity
• Antigen-presenting cells
• Helper T cells
– TH2
• B cells
• Plasma cells
APCs at work
Fig. 17.12
11/24/2017
8
Fig. 17.13
The result of helper T
cell activation is clonal
expansion.
Activation of B cells
• Binding of T-independent
antigens may activate B
cells, or
• B cells may process T-
dependent antigens
• Helper T cells co-
stimulation by interleukin-
2 or other cytokines
Antibody-mediated immunity(T dependent antigens)
Fig. 17.5
11/24/2017
9
The result of B cell
activation is clonal
expansion.
Fig. 17.20
Antibody structure
Fig. 17.4
Fig. 17.8
11/24/2017
10
Immunologic memory
Fig. 17.17
Types of adaptive immunity
Fig. 17.18