Chapter 43 ~

The Immune System

The 3 R’s- Reconnaissance,

Recognition and Response

Types of Immunity

Innate Defense – nonspecific barriers (skin, mucus) and chemical defenses

phagocytic cells Acquired Defense- highly

specific, only after exposure to the pathogen

Specific immunity includes lymphocytes and antibodies

Macrophage filled with pathogens

Lines of Defense- Nonspecific or Specific

Non-specific patrolling cells attack pathogens, but

don’t “remember” for next time leukocytes

phagocytic white blood cells macrophages, neutrophils,

natural killer cells, dendritic cells

Antimicrobial proteins Complement system Interferons

inflammatory response increase in body temp. increase capillary permeability attract macrophages/neutrophils

yeast

macrophage

bacteria

Specific defense Antigens illicit a response

of B or T cells Lymphocytes recognize a

small portion of the antigen called an epitope

After initial response- possible illness

Selected B cells clone themselves to become antibodies

Some B cell clones develop into memory cells

The Inflammatory Response 1- Tissue injury causes release of chemical signals 2. Histamine causes dilation and increased permeability of capillaries 3. Increased blood flow causes heat and swelling cytokines secreted by blood vessel endothelial cells initiate phagocytic migration of WBCs 4- Phagocytosis of pathogens occurs by WBCs

Acquired or Specific Immunity Terms B Cells- WBCs made in bone

marrow T Cells WBC stored in thymus Antigen: a foreign molecule that

elicits a response by lymphocytes Antibodies: antigen-binding

immunoglobulin, produced by B cells

Antigen receptors: plasma membrane receptors on B and T cells

Memory cells: cloned lymphocytes

Major Histocompatability Complex MHC

body cell surface antigens coded by a family of genes Allows cells to recognize each other as SELF Different antigens will be considered FOREIGN

Cell-mediated Response: T cells Cytotoxic T cells Destroy cells infected by intracellular pathogens and

cancer cells by cell lysis by the chemical perforin

Humoral response: B cells Occurs outside the

cell Helper T cell aids

macrophage with CD4 protein

Activated T cell secretes cytokines that activate B cell

B cell differentiates into memory and plasma cells (antibodies)

Helper T lymphocytes Function in both humoral & cell-mediated immunity Stimulated by antigens Clones itself and produces memory cells

How Antibodies work1. antibody binds to and blocks antigen activity

2. Agglutination: antigen clumping

3. Precipitation: cross-linking of soluble antigens

4. Complement fixation: activation of 20 serum proteins, that lyse viruses and pathogenic cells

Primary and Secondary Immune Responses

Primary Secondary -lag time of 10 days -no lag time

to 14 days as body - antibodies already makes antibodies made

- response is

immediate

Immunity in Health & Disease Active immunity:

natural: recovering from disease

artificial: immunization

Passive immunity:

natural: mother to fetus; breast milk

• artificial: rabies antibodies

Active Immunity Get exposed to pathogen!

Naturally – get sick Artificially – get a vaccination

Both methods cause memory cells to be made for future exposures.

Rapid response to

second exposure. You

don’t even know you

were exposed!

Naturally obtaining antibodies from mother

antibodies pass from mother to baby across placenta or in mother’s milk

Artificially injection of antibodies Ex: anti-venom serum short-term immunity

Passive immunity

Tissue Graft and Organ Transplantation

Can be a problem due to MHC

Antirejection drugs are used to prevent tissue or organ rejection

Identical twins have identical MHC but can have different antibodies (they aren’t always in the same place)

In 2013 a 3 year old has a 5 organ transplant- liver, stomach, pancreas small and large intestine

Abnormal immune functions

Allergies hypersensitive responses to environmental antigens (allergens);

Autoimmune disease (generate antibodies against own cells):

-multiple sclerosis (myelin sheath of nerve cells)

-lupus (variety of cells)

-rheumatoid arthritis (joints)

-insulin-dependent diabetes mellitus (pancreatic cells)

Immunodeficiency diseases:

- inborn -SCIDS (bubble-boy)

- acquired -AIDS

Acquired ImmunoDeficiency Syndrome

Immune system is susceptible to opportunistic infections ( a fungal pneumonia, Kaposi’s sarcoma)

Loss of helper T cells HIV is highly mutable Transmission requires

transfer of body fluids (semen and blood)

How Do Vaccines Work?

Vaccines imitate an infection

Immune system will respond by producing T cells and antibodies