Immune System

1. Define the following:a. B cells

b. T cells

c. Macrophages

2. Provide 3 cells and/or molecules involved in specific defense.

3. Provide 3 cells and/or molecules involved in non-speccific defense.

Innate Immunity

• What is innate immunity?• Present from birth• Non specific• External

– Skin– Mucous membranes

• Internal– Macrophages– phagocytes

Phagocytic cells

• Phagocytes bind to non-self surface carbohydrates

• microbe is engulfed forming a vacuole

• lysosome fuses with vacuole

• Evolution of microbes:– Extra capsule hides non-self surface

carbohydrates– Resistant to destruction by lysosomes

Pahgocytic Leukocytes

• Neutrophils: most abundant– Phagocytes that engulf and destroy microbes– Self destruct pus

• Monocytes: more effective– Macrophages– Reside mainly in lymph nodes, spleen and lymph

tissues• Eosinophils: less abunadant limited role

– Fight multicellular parasites• Dendritic cells:

– Stimulate aquired immunity

Antimicrobial Proteins

• Complement system

• Interferons– Secreted by virus infected cells– Induce other non-infected cells to release viral

inhibitors

• Defensins– Secreted by macrophages– Damage pathogens

Responses

• Localized inflammatory response

• Fever

• Septic shock – systemic inflamation

• Natural killer cells– Attack cancer and virus-infected cells

Lymphatic System

Acquired Immunity

Antigen Recognition

• What are the two main types of lymphocytes?– B cells– T cells

• There are antigen receptors on these cells

• Antigen receptors are specific for an epitope

B cell Receptors

• Y shaped with– 2 heavy chains– 2 light chains

• Recognize intact antigens

T cell Receptors• Recognizes self/non

self complexes– Pieces of antigens– MHC

• Class I MHC• Class II MHC

Lymphocyte development

• How do lymphocytes develop?

• Pleuripotent stem cells in bone marrow

• T cells migrate to thymus

• B cells mature in bone marrow

Lymphocyte Diversity

• 40 V chain options

• 5 J chain options

• How many different combinations of V/J arrangements are possible?

• 40 V x 5 J = 200

• How do we avoid auto immune issues?

• Before B cells and T cells mature, they are checked for class I and class II MHC compatibility.

• If they are compatible they are destroyed

Clonal Selection of Lymphocytes

• B cells, TH, and TC cells may be activated by finding their antigen in the body

• Binding of the antigen stimulated the cell to:– Generate short-lived clone of effector cells– Generate long-lived memory cells

Primary and Secondary Immunity

Humoral and Cell mediated Immunity

Helper T cells

Clone of TH cells

Clone of TH cells

Cytotoxic T cells

Humoral Immune Response

Antibodies

Role of Antibodies

Active and Passive Immunity

• What is the difference between active and passive immunity?

• Active immunity– Natural exposure to antigen– Immunization

• Passive immunity– Transferred antibodies– Seen with pregnant and nursing women– Also with anti-venom injections

Blood Groups

• Why would a person with type A blood have anti – B antibodies?

• There are bacteria with similar antigens• The immune response produced by blood group

antigens has no memory• Blood mixing at birth causes no problems fro

future pregnancies• Rh factors, however, do have memory so there

is a problem here• How do Rh negative mothers deal with blood

from Rh positive babies?

Allergic Response

Autoimmune Diseases

• Found in most body cells

• When infected or cancerous presents antigen fragments

• Identify the self/nonself complex

• Recognized by Tc cells

• Class II MHC found on – Dendritic cells– Macrophages– B cells

• Known as antigen presenting cells

Macrophage ingesting a yeast cell

Lining of trachea with orange mucus producing cells and yellow cilia