Immune System: Overview . The immune system has three types of components Lymphoid tissues Various types of immune cells Chemical signals that coordinate responses. Immune System: Functions . Protects against pathogens Bacteria Viruses Parasites
Number of active immune cells
Duct of eccrinesweat gland
keep hazardousorganisms andmaterials outsidethe body.
engulf pathogensand cell debris.
is the destruction ofabnormal cells by NKcells in peripheral tissues.
are chemical messengersthat coordinate thedefenses against viralinfections.
Interferons released by activatedlymphocytes, macrophages, orvirus-infected cells
consists of circulatingproteins that assistantibodies in thedestruction of pathogens.
1. Blood flow increased
2. Phagocytes activated
is a localized, tissue-levelresponse that tends tolimit the spread of aninjury or infection.
3. Capillary permeability increased
4. Complement activated
5. Clotting reaction walls off region
6. Regional temperature increased
7. Adaptive defenses activated
is an elevation of bodytemperature that acceleratestissue metabolism and theactivity of defenses.
Body temperature rises above 37.2ºC inresponse to pyrogens
Figure 24-4 (2 of 4)
Phagocyte forms pseudopods that
eventually engulf the particle.
Phagocytic vesicle is
fused with a lysosome.
Microbe in fused vesicle
is killed and digested by
lysosomal enzymes within
the phagolysosome, leaving
a residual body.
is removed by
Alpha ()-interferons areproduced by cells infectedwith viruses. They attractand stimulate NK cells andenhance resistance to viralinfection.
Beta ()-interferons,secreted by fibroblasts,slow inflammation in adamaged area.
Gamma ()-interferons,secreted by T cells and NKcells, stimulatemacrophage activity.
Viral nucleic acid
Interferongenes switch on.
Interferonbindingstimulates cell toturn on genes forantiviral proteins.
Host cell 2Binds interferon from cell 1; interferon induces synthesis ofprotective proteins
Host cell 1Infected by virus;makes interferon;is killed by virus
Figure 21.5, step 5
The formation of an antigen-antibody complex
Antibodies bind not to the entire
antigen, but to specific portions of
its exposed surface—regions
called antigenic determinant
Partial antigens, or haptens, do not
ordinarily cause B cell activation.
However, they may become attached to
carrier molecules, forming combinations
that can function as complete antigens.
The antibodies produced will attack both
the hapten and the carrier molecule. If
the carrier molecule is normally present
in the tissues, the antibodies may begin
attacking and destroying normal cells.
This is the basis for several drug
reactions, including allergies to
A complete antigen is an
antigen with at least two antigenic
determinant sites, one for each of
the antigen binding sites on an
Figure 24-4 (4 of 4)
to a receptor on a
specific B lymphocyte
(B lymphocytes with
form a clone
(can be years later)
Clone of cells
Neutralization – by binding to specific sites on the antigen, the antibody prevents its binding to cells
Activation of complement (nonspecific reaction) – when antibody bind to antigen, the Ab shape changes and that allows the binding of the complement proteins (which pathway?)
Fig. 1: Bacterial Adherence Via Pili
Fig. 1A: Blocking Bacterial Adherence with Antibody Molecules
Humoral immunityMechanisms of Antibody Action - summary
Fixes and activates
parts of bacterial
or to infant
in her milk
MHC classes – class I
MHC classes – class II