BIOL2300 Adaptive Immunity

Topics: Immune system, Major histocompatibility complex, B cell Pages: 49 (2550 words) Published: April 14, 2015
Adaptive Immunity

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Overview of Adaptive Immunity

• Adaptive immunity is the body’s ability to
recognize and defend itself against distinct
invaders and their products
• Five attributes of adaptive immunity






Specificity
Inducibility
Clonality
Unresponsiveness to self
Memory

© 2012 Pearson Education Inc.

Overview of Adaptive Immunity
• Involves activity of lymphocytes
• Two main types of lymphocytes
– B lymphocytes (B cells)
– Mature in the bone marrow
– T lymphocytes (T cells)
– Mature in the thymus
• Two types of adaptive immune responses
– Humoral immune responses works to eliminate extracellular antigens
– Bacteria, toxins, viruses in bloodstream, tissue fluids
– Cell-mediated immune responses deals with antigens
residing within a host cell
– E.g., invading virus infecting cell

© 2012 Pearson Education Inc.

Figure 16.1 A resting lymphocyte

Lymphocyte

Red blood cell

Elements of Adaptive Immunity
• Lymphatic System- major part of immune
system


A part of the circulatory system that screens tissues of the body for foreign antigens
– Composed of lymphatic vessels,lymphatic cells, tissues,
and organs
– Clear fluid flowing through lymphatic vessels is called
lymph made of white blood cells (lymphocytes) that helps
the body fight infection
– Lymph is similar to blood plasma and arises from the from fluid leaked out from blood vessels into surrounding tissues

© 2012 Pearson Education Inc.

Figure 16.2 The lymphatic system-overview

Elements of Adaptive Immunity

• The Tissues and Organs of the Lymphatic
System
– Lymphoid organs
– Primary lymphoid organs
– Red bone marrow
– Thymus

– Secondary lymphoid organs
– Lymph nodes
– Spleen
– Tonsils
– Mucosa-associated lymphatic tissue (MALT)
© 2012 Pearson Education Inc.

Elements of Adaptive Immunity

• Antigens
– Properties of antigens
– Molecules the body recognizes as foreign and
worthy of attack
– Recognized by three-dimensional regions called
epitopes
– Include various bacterial components as well as
proteins of viruses, fungi, and protozoa
– Food and dust can also contain antigenic particles

© 2012 Pearson Education Inc.

The Nature of Antigens
• Response to antigens varies depending on type
– Proteins and polysaccharrides generally elicit strong
response; lipids weak
– Small molecules usually not antigenic
– Terms antigenic and immunogenic used interchangeably
to describe ability of antigen to elicit immune response
• Epitopes trigger response
– Called antigenic determinants
– Regions of macromolecules
– E.g., 10 or so amino acids;
three-dimensional shapes
– Bacterial cell has multitude
of different epitopes
Antibodies

Epitopes
(antigenic
determinants)

Bacterial cell

Epitopes
(antigenic
determinants)

Elements of Adaptive Immunity
• B Lymphocytes (B Cells) and Antibodies
– Arise and mature in the red bone marrow
– Found primarily in the spleen, lymph nodes,
and MALT
– Small percentage of B cells circulates in the
blood
– Major function is the secretion of antibodies

© 2012 Pearson Education Inc.

Elements of Adaptive Immunity
• B Lymphocytes (B Cells) and Antibodies
– B-cell receptor (BCR) is membrane-bound version of a Bcell’s specific antibody; binding antigen triggers response – Usually needs confirmation from helper T cell
– Each B lymphocyte has multiple copies of the B cell
receptor
– The BCR is very specific
– Two variable regions of the BCR form the antigenbinding sites – Each BCR recognizes only one epitope
– Individual’s repertoire of BCRs is capable of
recognizing millions of different epitopes...
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