C3.2: Defense Against Diseases

Disease

Type of illness w/ characteristic symptoms

Causes (4)

1. Genetic - genetic disorders

2. environmental - toxins/radiation

3. Pathogens - organisms and viruses

4. Prion - Proteins that cause other proteins to misfold

Pathogens

Microorganisms that pass from one infected organism to another, they enter, multiply, and cause harm

Pathogen Types (4)

1. Bacteria - tuberculosis, leprosy

2. Fungi - athlete's foot

3. Protista (single-celled prokaryote) - malaria, sleeping sickness

4. Viruses (non-living) - influenza, measles, ebola

First Line of Defense

includes skin and mucus membranes

Skin

physical barrier that keeps pathogens out, layer of dry/thick/dead cells containing keratin

Sabaceous Glands

secretes lactic acid to make skin slightly acidic and inhibit microbial growth

Mucus Membranes

protects internal structures (ex. esophagus, trachea, genitals)

they are ciliated and secrete mucus (to trap and swallow/expel)

Ciliated

property of mucus membranes, have little cilila to move stuff and remove pathogens via coughing

Lysozyme

mucus membrane contains these, they are antiseptic that causes lysis in bacteria cell walls

Blood Clotting (hemostasis)

repairs damaged blood vessels in a cut, prevents blood loss and limits pathogen entry

Platelets

First step of blood clotting, they are blood cell fragments that change structurally to form a temporary "plug" of sticky, semi-solid gel

*they release clotting factors that eventually form insoluble mesh (scab)*

Coagulation Cascade Process

1. inactive prothrombin becomes active thrombin

2. thrombin converts soluble fibrinogen to insoluble fibrin

3. fibrin forms a blood clot that traps cells and seals wound

4. when exposed to air, blood clot forms a scab

5. after damage repaired, plasmin dissolves clot and scab

Leukocytes

white blood cells

Second Line of Defense (2)

Non-specific - responds to broad array of pathogens

Non-adaptive - responds in the same way, every time

Phagocytes

type of leukocyte that patrols blood and eats pathogens via endocytosis

ex. macrophage

Endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

Histamine

a compound that is released by cells in response to injury and in allergic and inflammatory reactions, causing contraction of smooth muscle and dilation of capillaries.

Chemotaxis

movement by a cell or organism in reaction to a chemical stimulus

Second Line of Defense Process

1. Phagocyte's pseudopodia engulfs pathogens

2. traps pathogens in vesicles

3. Fuses vesicle w/ lysosomes to form phagolysosomes (dissolves bacteria)

4. presents antigens (fragments of pathogen) on surface to initiate 3rd line of defense

Pseudopodia

part of phagocytes that helps to entrap pathogen

Phagolysosome

fusion of vesicle w/ pathogen and lysosome, allows of pathogen destruction

3rd Line of Defense (2)

Specific - differentiates between pathogens and alters response

Adaptive - builds memory to respond faster to same pathogen

*lymphocytes*

Lymphatic System

where white blood cells travel, consists of nodes and vessels

Function: manage fluid levels in body, returns fluid (lymph) leaked from circulatory system back to it via nodes

Antigen vs. Antibody

Antigen: "them"

-glycoproteins found on pathogen/cell surface, elicits immune response (antibody production)

Antibodies: "us"

-protein made by lymphocytes

-complimentary in shape and charge to antigens

-binding between the two is irreversible

More on Antibodies

-produced by lymphocytes, each lymphocyte can only produce one type (b/c clone)

-made up of 4 polypeptides

-makes pathogen more recognizable to phagocytes

-prevents viruses from docking to host cells

Opsonization

An immune response in which the binding of antibodies to the surface of a microbe facilitates phagocytosis of the the microbe by a macrophage

Opsonin

an antibody or other substance that binds to foreign microorganisms or cells, making them more susceptible to phagocytosis.

Antibody Regions (2)

Hypervariable: binding site of antigens from phagocytes or pathogens or random antigens floating around

Constant: helps body fight pathogen (able to be recognized by B-cell)

Types of Lymphocytes

1. B-cells, made in bone marrow, produces antibodies

2. Helper T-cells, matures in Thymus, activates B-cells and cytotoxic T-cells

3. Cytotoxic T-cells, destroys body's own cells that have been infected or become cancerous

After Antigen Presentation in Phagocytes...

antigens bind to and activate specific helper-t cells that have complimentary antigen receptors

activated helper t-cells then activate helper specific B-cells

How do Helper T-cells activate B-cells?

By releasing cytokines or through direct contact

Cytokines

type of ligand released by Helper-T cell to activate B-cell

Activated B-cell Differentiation

Plasma B-Cells or Memory B-cells

Effector Cell

A short-lived cell, what a Plasma B-cell is

Plasma B-cell

A short lived cell that produces high amounts of specific antibodies

They develop extensive rER and golgi to assist in protein synthesis

*die after infection overcome*

Memory B-cells

Remain inactive until same pathogen enters system, then activate and respond rapidly by stimulating production of Plasma B-cells

Immunity

Either having antibodies to pathogen or memory B-cells that can rapidly produce antibodies

Cytotoxic T-cells

destroys pathogens and body's own infected cells by secreting perforating proteins to puncture cell membrane and induce cell lysis

Antibody Relevance in pathogen removal

Produced by plasma b-cells, then tag antigens of pathogens by binding to it with hypervariable region. Constant region then attracts macrophages (phagocytes) for pathogen destruction

HIV Transmission

Occurs via exchange of body fluids

1. unprotected sex w/ abrasions

2. shared usage of hypodermic needles

3. blood transfusions or blood products

4. childbirth and breastfeeding

HIV (General Facts)

A RNA retrovirus that synthesizes DNA with reverse transcriptase

How to inhibit HIV (2)

1. Use antiretroviral drugs to inhibit reverse transcriptase

2. Use drugs that target HIV enzymes utilizes in DNA entry

How HIV affects the immune system

It destroys Helper T-cells, meaning that the CD4+ receptor can no longer recognize antigens on pathogens

Therefore no activated B-cells (no antibodies) or no activated cytotoxic T-cells

Host eventually killed by opportunistic infections (bc can no longer respond normal infections w/ 3rd line of defense)

AIDS

Acquired immunodeficiency syndrome

Syndrome is a collection of symptoms and infections

Kaposi's Sarcoma, a marker disease (if u have Kaposi's Sarcoma, then u likely have HIV)

Bactericidal vs. Bacteriostatic

Bactericidal - Kills bacteria

Bacteriostatic - Inhibits bacterial growth

Antibiotics

Kill and/or inhibit growth of bacteria

Target prokaryotic DNA replication, protein synthesis, enzymes, 70S ribosomes, and cell wall formation

*don't affect eukaryotes bc of structural and metabolic differences*

*don't affect viruses bc viruses are non-living and have no metabolism*

Narrow vs Broad Spectrum

Narrow Spectrum - effective against specific bacteria

Broad Spectrum - effective against many types of bacteria

Fleming (1928)

Identified penicillin, first chemical antibiotic

Penicillin

Produced by saprotrophic fungi that competed with saprotrophic bacteria, inhibits bacterial competitors via secretion

Florey and Chain (1940)

first clinical trials of penicillin

Antibiotic Resistance

Only a concern if strains with multiple resistances develop (such things are now widespread.

Easy for bacteria to get bc of horizontal gene transfer using plasmids (can just transfer resistance gene)

MRSA

Methicillin-resistant Staphylococcus aureus)

Example of strain with multiple resistances

**superbacteria**

Measures to Prevent Antibiotic Resistance (5)

1. Prescribe antiobiotics for only serios bacteria

2. Maintain high level of hygiene to prevent cross infection

3. Farmers must exclude antibiotics from animal feeds

4. Develop new antibiotics

5. Do not overuse antibiotic products

Zoonoses

Type of pathogen that can cross from species (zoonotic pathogen)

*most pathogens species specific*

Zoonoses Examples

Mycobacterium bovis (cows)

Lyssaviruses (rabies)

COVID-19 (bats)

Immunity Xtra Info

Having Memory B-cells that, if second infection, can quickly produce plasma B-cells to produce antibodies

Prevents disease from really developing

Vaccinations

Promotes immunity by producing memory B-cells

given via intramuscular or subcutaneous (skin) injections

Contains some form of pathogen (weakened/killed pathogen, subunits of pathogen like antigen, or mRNA that codes for antigen)

Epidemic

increase in prevalence of infection within a region

Pandemic

Epidemic that has spread over a larger area

Herd Immunity

Spread of pathogen is impeded because of its repeated encounters with people who are immune, can protect individuals that cannot be vaccinated.

Created via vaccination or those who have already had the disease

Herd Immunity Equation

(1-1/r) * 100%

R is the average number of people that the infected person infects