Microbiology unit 5 - Immune system

Non-specific defenses

• Work against all types of microbes

• 1st + 2nd line defenses

Specific defense

• Targeted at specific microbes

• 3rd line defense

Innate defenses

• Born with these

• 1st + 2nd line defenses

Adaptive defenses

• Develop over time

• 3rd line defense

1st line defense

• Found mostly where body contacts environment

• Barriers to microbial access

What 2 body parts are 1st line defenses

1. Skin

2. Mucus membranes

Skin

• Physical barrier to microbes

• oils, salt, nmb inhibit microbes

Mucus membranes

• Trap microbes

• phagocytes + antibodies also in mucus membranes

• Form linings of gastrointestinal, respiratory, urogenital tract

2nd line defense

• Generally found inside the body

• Go to work once microbe has gained access

What are 3 examples of the 2nd line defense

• Phagocytes

• Inflammation

• Fever

Phagocytes

• engulf + usually engulf potential pathogens

• Can leave blood and enter tissue fluid

3 examples of phagocytes

1. Macrophages

2. neutrophils

3. eosinophils

Inflammation

• Caused by tissue damage (not always microbial)

• Causes increased levels of key defense proteins

• Brings phagocytes and other defenses to area

• Redness, pain, heat, and swelling

Fever

• systemic response

• Increased temperature slows microbial growth

• increases production of disease-fighting T-cells

• extreme fever (>105) is harmful: dehydration, brain damage

interleukin-1

• chemical released by phagocytes in response to different microbial chemicals

• Causes fevers

3rd line defense

found in blood, lymph, tissue fluid, mucus

1 red blood cells =

250 million hemoglobin molecules

3 parts of 3rd line defense

1. B-lymphocytes

2. T-lymphocytes

3. Antibodies

B-lymphocytes

• white blood cells

• makes circulating antibodies

T-lymphocytes

• white blood cells that mature in thymus

• fight intracellular pathogens

• coordinate immune system

Antibodies

• protein molecules

• bind to antigen that caused their production

lymphatic system is a key part of the

1. circulatory system

2. immune system

7 parts of lymphatic system

1. Bone marrow

2. thymus

3. spleen

4. lymph nodes

5. lymph vessels

6. tonsils

7. appendix

What leaks from capillaries into spaces between cells

Blood plasma

What absorbs blood plasma fluid and circulate it in the system

lymph vessels

What are lymph nodes filled with

white blood cells

what do white blood cells do in the lymph nodes

screen lymph fluid for invaders (microbes)

interstitial fluid

• intercellular/tissue fluid

• plasma that leaks from capillaries

Capillaries leak about how much of the plasma that flows thru them

1%

Lymph fluid

Name for some plasma that enters the “dead end” lymph vessels

Lymph vessels have

valves that prevent lymph fluid from flowing backward

lymph nodes

lymph vessels empty into these sac-like organs

what do lymph nodes contain

immune system cells

Lymph fluid continues to circulate “forward” until it reaches what

lymphatic ducts

lymphatic ducts

• empty into large veins near the heart

• returns fluid to the blood

bone marrow contains what type of cell

stem cells

Stem cells give rise to

• red blood cells

• white blood cells

leukocyte

white blood cells

2 types of white blood cells

• phagocytes

• lymphocytes

Antigen

• any foreign molecule that causes antibody production (immune response)

• unique to microbe

Circulating antibodies

Antibodies made and secreted by B-cells

3 types of Circulating antibodies

1. IgA

2. IgG

3. IgM

Bound antibodies

Antibodies embedded in the plasma membrane of B-cells and T-cells

Type of bound antibodies

IgD

opsonization

Antibodies mark microbes and enhances phagocytosis

6 ways binding antibodies inactivates antigens

1. neutralization

2. agglutination

3. inflammation

4. cell-mediated cytotoxicity

5. activation of complement

6. opsonization

Human genome has about

30,000 genes

Human body can produce about how many different antibody molecules

500,000 antibody molecules

Utero

B-cell maturation

During B-cell maturation (utero), what is shuffled in the antibody gene

nucleotide sequence

antigenic specificity

shape, contours, and fit unique to each antibody

IgD constant region

anchors antibody in membrane

IgD variable region

face out towards environment

How many IgD molecules are in B-cell plasma membrane

Thousands

Clonal selection

begins after a B-cell contacts an antigen that binds its IgD molecules

What 3 key events occur after the antigen-antibody binding of a B-cell

1. Plasma cell formation

2. Memory cell formation

3. Antibody production

Plasma cells

secrete antibodies (IgM, IgG, IgA)

Plasma can secrete how many antibodies per second

~2,000 antibody molecules per second

Memory cells

• don’t secrete antibodies

• identical to parent B-cell

• long-term immunity

Apoptosis

• Programmed death

• Plasma cells die when infection passes

Where do memory B-cells locate to

1. lymph nodes

2. spleen

primary immune response

• occurs first time a particular antigen is encountered

• slow + takes time

• OG B-cells

secondary immune response

• occurs when same antigen (MO) is encountered again

• faster + takes less time

• Memory cells

main reason for vaccination

• make memory cells

• immune response will be faster if the real pathogen is encountered

Humoral immunity

• Defenses against microbes outside of cells

What is humoral immunity provided by

1. B-cells

2. Antibodies

Humors

• blood

• lymph

• tissue fluid

• mucus

2 main sections of immune system

1. Humoral immunity

2. Cell-mediated immunity

Cell-mediated immunity

• Defenses against microbes inside cells (viruses)

What is cell-mediated immunity provided by

T-cells

Which 2 types of immunity does T-cell coordinate the activities of

1. Humoral immunity

2. Cell-mediated immunity

Antigen presenting cells

• WBCs take in antigens

• “display” antigens on plasma membranes

2 types of Antigen presenting cells

1. Macrophages

2. Dendritic cells

Cytokines

Non-antibody proteins secreted by stimulated WBCs

Cytokines stimulate WBCs to act in what 3 ways

1. APCs make cytokines that attract B-cells & T-cells

2. Causes B-cell and T-cell proliferation after antigen activation

3. Cause activated B-cells to secrete antibodies

Helper T-cells can secrete how many different cytokines

30 different cytokines

Helper T-cells

• secrete B-cell growth factor

• secretes cytokines that lead to the development of activated cytotoxic T-cells

B-cell growth factor

• cytokine

• Signals antigen-activated B-cells to form plasma cells and memory cells

Suppressor T-cells

secrete cytokines that suppress B- and T-cell activity when antigen is gone

Cytotoxic T-cells

cells kill host cells with pathogens inside

What do cytotoxic T-cells secrete once they bind to infected cells with their IgD moleluces

Perforin

Perforin

• toxic protein

• punctures plasma membrane of infected cell

• infected cell lyses

Death of the infected cell caused by cytotoxic T-cells releases

pathogens into bodily fluids

Once the pathogen is released into bodily fluids

Circulating antibodies (humoral immunity) and phagocytes are now able to fight pathogen

4 types of immunity

1. Naturally acquired active immunity

2. Artificially acquired active immunity

3. Naturally acquired passive immunity

4. Artificially acquired passive immunity

Naturally acquired active immunity

• Immunity received from having the illness

• when MO causes a natural infection

• long-lasting

Artificially acquired active immunity

• Immunity through immunization

• long-lasting immunity

Naturally acquired passive immunity

• When a fetus or infant gets immunity from mom

• mother’s antibodies passed to baby

• through placenta/during nursing

• only for illnesses mother is immune to

Artificially acquired passive immunity

• pre-formed antibodies form another animal are injected into the body

• Immune serum globulin, anti-toxins, anti-venoms

• temporary protection