CHAPTER 17 Adaptive immunity: Specific defenses of the host

Humoral immunity

• AKA antibody mediated immunity

• Directed at freely circulating pathogens

• Depend on B cells

Cellular immunity

• depend on T cells

• Eliminate intracellular pathogen

• Reject foreign tissue

• Destroy tumor cells

B cells mature in

Bone marrow

Humoral immunity B cells

• Recognize antigens

• Make specific antibodies

Cellular immunity produces

T lymphoctes (T cells)

T cells mature in

Thymus

T cell receptors

Contact antigens and secrete cytokines

Cellular immunity attacks

Antigens that have already entered cells

• M leprae

• L monocytes

Humoral immunity fights

Invaders and threats outside cells

Antigen

• Substances that causes the body to produce specific antibodies

• Protein or large polysaccharaides

Hapten

Low molecular weight antigen

Antibodies

Globular proteins called immunoglobulins

Bivalence

Antigen binding sites

Y shaped monomers

• IgG

• IgD

• IgE

2 or 3 monomers

• IgA

• IgM

IgG

• enhance phagocytosiS

• Trigger complement system

• Neutralize toxins

• ProteCT’s fetus and newborn

• Blood, lymph, and intestines

IgM

• Blood, lymph, and B cells

• Clumper

• First response to an infection

IgA

• Prevents microbial attachment to mucous membrane

• Resistance against intestinal and respiratory pathogens

IgD

• blood, lymph, and B cells

• No well defined function

IgE

• releases histamines

• Respond to allergic reaction

• Lysis of parasitic worms

Inactive B cells contain

Immunoglobulins that bind to antigen

• IgM and IgD

B cells that need to be activated produce

• 1 plasma cell

• 2 memory cells

B cell becomes activated when

Ig binds to epitope

T dependent antigens

T helper cells

major histocompatibilty complex

Encode molecules on the cell surface

MHC classes

• Class 1 - on membrane of nucleated animal cells

• Class 2 - surface of antigen presenting cells

Clonal selection

Differentiates B cells into

• antibody producing plasma cells

• Memory cells

T independent cells

• no T cell help

• Repeated subunits (polysaccharides or liposaccharaides)

• Weak response

• NO memory cell

Antigen antibody complex

Antibodies bind to antigen

Antigen antibody complex protects host by

Tagging foreign molecules for destruction

Results of Ag-Ab binding

• agglutination

• Opsonization

• Antibody dependen cell mediated cytotoxicity

• Neutralization

• Activation of the complement system

Agglutination

Reduces number of infectious units

Opsonization

Coats antigen with antibody

Complement fixation

Causes inflammation and cell lysis

AB dependent cell mediated immunity

Causes destruction by macrophages

Neutralization

Blocks adhesion of bacteria

Different kinds of T cells

• T helper cells

• T cytotoxic cells

• T regulatory cells

T cells respond to antigen by

T cell receptors

Recognition of antigen via a T cell requires

Antigen presenting cells

T cells are also lassitude on their surface by

Clusters of differentiation

Th cells produce cytokines an separate into

• Th1

• Th2

• Memory cells

Th1

Produces IFNy

• activates cells for cell mediated immunity

Th2

Activates eosinophils and B cells to produce IgE

CD8+ or Tc cells

Targets altered host cells (tumor cells)

Cytotoxic t lymphocytes

Induces apoptosis in target cell

Cytotoxic tlymphocytes releases

Performing and grandzymes

Treg cells

CD4 and CD 25 on surface

T regulatory cells

• suppresses immature T cells that escape deletion in the thymus

• Protects intestinal bacteria from immune system

• Protects fetus from rejection

Antigen presenting cell

Digests antigen

Antigen fragments on APC surface

• B cells

• Dendritic cells

• Activated macrophages

Chemical messengers

Glycoproteins that are produced by all cells of the immune system in response to a stimulus

Overproduction of Cytokine leads to

Cytokine storm

Cytokine storm causes

Damage to tissues

Antibody titer

Amount of antibody in serum - reflects intensity of the humoral response

Primary response

Occurs after initial contact with antigen

Secondary response

Occurs after second exposure

Naturally acquired active immunity

Resulting from infection

Naturally acquired passive immunity

Transplacental or via colostrum

Artificially acquired active immunity

Injection of antigen like vaccination

Artificially acquired passive immunity

Injection of antibody