Chapter 15: The Adaptive
Immune Response
General Characteristics of the
Adaptive Immune Response
• Involves specialized WBC’s known as
lymphocytes
• Response is highly specific (molecular
specificity)
• Response generates memory
• Can discriminate between self and non-self
(tolerance)
Overview of the Adaptive Immune Response
Anatomy of the Lymphoid System
• Lymphatic Vessels
– form lymph
• Secondary lymphoid Organs
– Lymph nodes, spleen, tonsils,
peyer’s patches
• Primary Lymphoid Organs
– Bone marrow and thymus
Peyer’s Patch is example of
secondary lymphoid organ
Lymphocytes are responsible for the
adaptive immune response
What promotes an immune response?
• Antigens
– Any molecule that reacts with antibody, B cell
receptor or T cell receptor
– Composition is usually proteins or
polysaccharides
– Foreign substance with MW of 10,000 daltons
– Examples of antigens: bacterial capsules, cell
walls, flagella, toxins of bacteria
Antibodies bind antigens
Small molecules are not recognized as
antigens until bound to another
How are antigens recognized?
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Self markers also known as MHC markers
MHC (major histocompatibility complex)
MHC Class I-produced by all body cells
MHC Class II-produced by dendritic cells,
B cells, and macrophages
– These cells are also called antigen presenting
cells (APCs)
How are B cells
activated?
B cell activation by Helper T cell
Structure of an antibody
There are 5 classes of antibodies
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•
•
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IgM
IgG
IgA
IgE
IgD
Immunoglobulins
Naïve B cells produce IgM, then
IgG antibodies
Primary and secondary response to antigen
What can happen when antibody binds antigen?
T-independent antigens activate
B-cells without T cells
Let’s look at the T cells
• Have own T cell receptor (TCR)
• Do not make antibodies
• Must recognize MHC markers which
“present” antigen
T cells differ from B cells
• Must use MHC markers on host cells to
recognize antigens
Antigen recognition by T cells
occurs with MHC:TCR binding
How are T cells activated?
Effector functions of Cytotoxic T cells
Effector function of Helper-T cells
Effector function of Helper-T cells
Natural Killer
Cells…lymphocyte but not a T
cell
Antibody dependent cell
mediated cytotoxicity