Chapter 14 Micro

dude

Functions of a healthy functioning immune system

Surveillance, recognition, destruction

Innate, natural defenses

present at birth, provide nonspecific resistance to infection

Adaptive immunities

specific, must be acquired

First line of defense

any barrier that blocks invasion at the portal of entry – nonspecific

Second line of defense

protective cells and fluids; inflammation and phagocytosis – nonspecific

Third line of defense

acquired with exposure to foreign substance; produces protective antibodies and creates memory cells – specific

First line of defense: Physical barriers

• Skin

• Tears, saliva, urine flush out microbes

Defense of respiratory tract

• Mucous coat impedes attachment and entry of bacteria

• Nasal hair traps larger particles

Lysozyme

an enzyme that hydrolyzes the cell wall of bacteria, in tears

Some hosts are genetically _____ to the diseases of other hosts

immune

antigen

A substance that induces the production of antibodies

Antibodies

Proteins secreted by our immune cells that bind antigens

White blood cells (WBCs) include

Leukocytes and lympocytes

Granulocytes/Agranulocytes

innate capacity to recognize and differentiate any foreign material.

Lymphocytes

adaptive immunity and are used recognize and differentiate any foreign material

Nonself

is foreign material

Self

normal cells of the body

Pathogen recognition receptors (PRRs)

• receptors on WBCs (ex: neutrophils)

• epithelial cells for PAMPs (ex: toll-like receptors)

T-Lymphocytes and B-Lymphocytes/plasma cells are adaptive/innate immunity

adaptive

Basophils, eosinophils, neutrophil, macrophage, etc are adaptive/innate immunity

innate

Hemopoiesis/Hematopoiesis

production of blood cells

Stem cells

undifferentiated cells, precursor of new cells

Embryonic stem cells are

totipotent ~ can become any cell in the body

Hematopoietic stem cells are

multi-potent ~ can give rise to a limited number of cell types

Granulocytes

contain cytoplasmic granules, have lobed nucleus

Agranulocytes

do not contain granules, have unlobed rounded nucleus

Neutrophils

first immune cell to arrive upon infection, initiate inflammatory cascade upon encountering foreign material

Neutrophils makes up

55-90% of all immune cells

Eosinophils

• destroy eukaryotic pathogens particularly round worm infections

• IgE (antibody) mediated degranulation and allergy response

Eosinophils make up

1-3% of all immune cells

Basophils

release potent chemical mediators and IgE (antibody) in allergy responses

Basophils make up

0.5% of immune cells

Mast cells

• Nonmotile cells bound to connective tissue

• Participates in IgE mediated allergy responses

• Attract phagocytes to the site of infection

Monocytes, Macrophages, & Dendritic cells

• kidney-shaped nucleus; highly phagocytic and can present antigens

• Largest of WBCs

Monocytes, Macrophages, & Dendritic cells make up

3-7% of the immune cell population

Monocyte

earliest stage, pre-curser cell type to macrophages & dendritic cells

Macrophages

final differentiation of monocytes

Dendritic cells

trap pathogens and participate in immune reactions by “professional antigen presentation”

Sort from least phagocytic/ability to present antigens

monocytes, macrophages, dendritic

Lymphocytes make up

20-35%

Lymphocytes

specific immune response

Innate immunity: Natural Killer T Cells

kill pathogen infected host cells

Adaptive immunity - Humoral immunity: Memory B cells typically provide long/short lasting immunity

long

Adaptive immunity - Humoral immunity: Plasma B cells produce

antibodies

Cytolytic T cells

kill foreign cells

Helper T cells

modulate immune functions

T regulatory cells

down regulate the immune response

Memory T cells

long lived cells that will recognize pathogens later

Erythrocytes

develop from bone marrow stem cells, no nucleus, simple biconcave sacs of hemoglobin.

Platelets

formed elements in circulating blood that are not whole cells

Lymphatic System Purpose

1. Provides an auxiliary route for return of extracellular fluid to the circulatory system

2. Acts as a drain-off system for the inflammatory response

3. Renders immune surveillance, recognition, and protection against foreign material by trafficking immune cells

Lymphatic capillaries permeate all parts of the body except

CNS, bone, placenta, and thymus

Lymphatic Vessels

• Functions to return lymph to circulation

• Thin walls easily permeated by extracellular fluid which is then moved through contraction of skeletal muscles

Primary lymphatic organs purpose

generates the lymphocytes and early immune cells

Ex: Red bone marrow and thymus gland

Secondary lymphatic organs

site of educating lymphocytes and immune cells

Ex: lymph nodes and spleen

Red bone marrow

• Site of blood cell production

• Some white blood cells mature here (B cells)

• More bones in children have red marrow and it decreases as we age

Thymus gland

• Site of T cell maturation

• Bilobed gland found in the thoracic cavity superior to the heart

• Largest in children and shrinks as we age

• Immature T lymphocytes move from the marrow to the thymus where they mature

The primary lymphatic organs are

Red bone marrow and thymus gland

Lymph nodes

Small, oval-shaped structures found along the lymphatic vessels filled with B cells, T cells, macrophages, and dendritic cells

Spleen

filters circulating blood to remove worn out RBCs and pathogens; structurally similar to lymph node

Gut associated lymphoid tissue (GALT)

Specialized lymphoid tissue in the gastrointestinal tract to increase rate of processing intestinal antigens

Examples of secondary lymphatic organs and sites of Antigen presentation

Lymph nodes, spleen, GALT

Second Line of Immune Defense (process)

1. Recognition by innate immune cells

2. Initiate Inflammation

3. Phagocytosis of foreign microbe or infected cells

4. Complement to increase phagocytosis and lyse microbial membranes

5. Interferon to alert a specific immune attack

Pattern Recognition Receptors (PRRs)

Proteins on the cell surface of innate immune cells and epithelial cells

Pathogen associated molecular patterns (PAMPs)

are unique molecules that identify microbes as non-self

• Lipolysaccharides

• Double stranded RNA

• Peptidoglycan

-molecules shared by microorganisms

Cells expressing PRRs then will secrete ______ & _______ chemical signals to alert the immune system

cytokines & chemokines

Cytokines

alert the immune system to distinguish the type of infection

Chemokines

chemical signal that will induce chemotaxis or trafficking of immune cells to the site of infection

Redness

increased circulation and vasodilation in injured tissues in response to chemical mediators

Warmth

heat given off by the increased blood flow, can lead to fever

Swelling

increased fluid escaping into the tissue as blood vessels dilate – edema; WBC’s, microbes, debris, and fluid collect to form pus (abscess); prevents spread of infection

Pain/soreness

stimulation of nerve endings

Diapedesis

migration of cells out of blood vessels into the tissues

Chemotaxis

migration in response to chemokines

Fever is initiated by

pyrogens

Fever (definiton)

Initiated by circulating pyrogens which reset the hypothalamus to increase body temperature; signals muscles to increase heat production and vasoconstriction

Exogenous pyrogens

products of infectious agents

Endogenous pyrogens

liberated by monocytes, neutrophils, and macrophages during phagocytosis

General activities of phagocytes

1. To survey tissue compartments and discover microbes, particulate matter, and dead or injured cells

2. To ingest and eliminate these materials

3. To extract immunogenic information (antigens) from foreign matter to present to other immune cells

Complement

blood proteins that work in concert to destroy bacteria and viruses

Complement (process)

1. Recruits phagocytes

2. Opsinize pathogen surfaces causing phagocytosis

3. Membrane attack complex

Membrane attack complex

makes holes in some bacteria and viruses that causes them to burst

Opsinization

binding of antibodies or complement proteins to the surface of infected cells or directly to the microbes.

Steps of opsinization

increases the rate of phagocytosis → increases antigen presentation → increases clearance of the microbe

Complement Pathways - Classical

activated by the presence of antibody bound to microorganism

Complement Pathways - Lectin pathway

nonspecific reaction of a host serum protein that binds mannose (sugar) on bacterial surface

Complement Pathways - Alternative

begins when complement proteins bind to cell wall and surface components of microorganisms

Binding of antibodies, mannose, or bacterial surface molecules activates…

Complement pathway

Interferon

Small protein produced by certain WBCs and tissue cells

Interferon alpha

lymphocytes and macrophages

Interferon beta

fibroblasts and epithelial cells

Interferon gamma

T cells

Interferons are produced in response to

viruses, RNA, immune products, and various antigens