Immune system & response unit 2 cell biology Y12

What is the non-specific immune system?

The non-specific immune system is the body's first line of defense against pathogens, providing immediate responses that do not target specific invaders.

What is a pathogen?

A microorganism that causes disease

What are types of pathogen?

• bacteria

• Fungi

• Protists

• Virus

What are antigens?

they bring out an immune response due to the foreign proteins entering the body

What are antigens usually?

Proteins, polysaccharides or glycoproteins are

Why are some transplanted organs rejected by the body?

Due to the transplanted organ’s foreign antigens which trigger an immune response

What drugs are taken to prevent rejection?

Immuno-suppressants

What do phagocytes do?

1. They are attracted to the pathogen by the pathogen’s chemical products

2. The phagocyte’s receptors attach to the chemicals on the surface of the pathogen

3. Lysosomes in the phagocyte migrate towards the phagosome formed by engulfing the pathogen using phagocytosis

4. They then digest these pathogens using enzymes called lysozyme and the pathogens products are absorbed by the phagocyte

What are some features of phagocytes?

• an elongated nucleus

• A fluid shape to move the pathogen

What is chemotaxis?

The phagocyte being chemically attached to the pathogen

What are physical barriers in the non-specific immune system?

• skin

• Nose hairs

• Stomach acid

What is phagocytosis?

Phagocytosis is the process by which certain immune cells, like macrophages, engulf and digest pathogens.

What are 3 types of phagocyte?

• neutrophils

• Macrophages

• Mast cells

What role do neutrophils play in the immune response?

Neutrophils are white blood cells that rapidly respond to infections, particularly bacterial infections (due to chemotaxis) by ingesting and destroying pathogens.

How does inflammation contribute to the non-specific immune response?

Inflammation increases blood flow and immune cell recruitment to the site of infection, helping to isolate and eliminate pathogens.

What is a key characteristic of the non-specific immune response?

The non-specific immune response is rapid and does not involve memory, meaning it responds the same way to repeat infections.

What is the specific immune system?

The specific immune system is the part of the immune system that provides targeted responses to specific pathogens, developing memory for future encounters.

What is the function of the specific immune system?

To provide targeted responses to specific pathogens and develop immunological memory.

What does the specific immune system contain and what do these do?

It contains different types of lymphocytes which can distinguish between different types of microbe

• they respond slower than phagocytes but have a memory causing them to have a faster response by a reoccurring infection (immunological memory)

What are the two different divisions in the specific immune system?

• antibody mediated immunity (humoral immunity)

• Cell mediated immunity

What cells are primarily involved in the specific immune response?

B cells and T cells

Where do these cells mature?

• b cells mature in the bone marrow

• T cells mature on the thymus gland

What does humoral immunity do?

• makes B cells which mature in the bone marrow

• The B cells respond to foreign antigens on bacteria, viruses and bacterial toxins by producing specific antibodies

How do B cells respond to pathogens?

Each B cell only makes 1 type of antibody to act as a receptor to the antigen they’re complimentary to

What happens when the B cell binds to the pathogen?

The b cells activated and copies itself millions/ thousands of times to defeat all of that pathogen

What is the role of T cells in the specific immune system?

T cells help in directly killing infected cells (cytotoxic T cells) or assist other immune cells (helper T cells).

What are antibodies?

Proteins produced by B cells that specifically bind to antigens to neutralize pathogens.

What are the 2 types of antibody?

Agglutinin and Opsonin

What does agglutinin do?

They make pathogens stick together which immobilises them so they can’t enter just cells and reproduce

What do opsonin do?

They stimulate phagocytes to engulf the pathogens so they can more easily recognise, track down and ingest the pathogens

What is the role of cell mediated immunity?

• involves cells that attack foreign substances directly using T cells

What do T cells do?

• They mostly attack infected body cells

• They can special membrane bound receptor proteins on their surface which enable them to recognise and bind with complimentary antigens

What are the 2 types of T cells?

• helper T cells

• Cytotoxic T cells

What do helper T cells do?

• they secrete lymphokines to activate other cells in the immune system

• They attract and stimulate macrophages (enhancing phagocytosis)

• B cells aren’t active if T cells aren’t present

What do Cytotoxic T cells do?

• they attach to pathogens directly or cells infected by pathogens

• Once attached, they release the chemical perforin which perforates (puts tiny holes in) the foreign cell, bringing about lysis

What is an antigen-presenting cell (APC)?

A cell that displays foreign antigens on its surface to stimulate B cells to divide

What is the difference between active and passive immunity?

Active immunity involves the immune response to a pathogen, while passive immunity is the transfer of antibodies from another source.

What is a memory cell?

A long-lived immune cell that helps the body quickly respond to previously encountered antigens.

What happens in the primary response?

• takes 3-14 days (latent period) to produce antibodies

• Memory cells produced by mitosis of B cells and retain ability to secrete antibodies

Why does it take so long to produce antibodies?

Because the B cells must be activated by the foreign antigen and the right b cell must fit the shape of the foreign antigen

What happens in the secondary response?

• memory cells allow smaller amounts of antigens needed to stimulate response

• Memory cells divide quickly to increase number of cells secreting antibodies

• B cells clone to form plasma cells

• T cells clone to form mostly helper and cytotoxic cells

What is different about the primary response to the secondary response?

The primary response is slower

The secondary response is faster and has a shorter latent period due to the memory b cells and antibody production is faster and greater

What is antigenic variability?

When one virus can exist in many forms and each new form contains a different antigen

Why can is be difficult to develop a vaccine against some viruses?

Because of antigenic variability

What is vaccination?

The introduction of a weakened or inactive pathogen or its antigens to stimulate an immune response and memory formation.

What are the 4 types of immunity?

• active natural immunity

• active artificially induced immunity

• passive natural immunity

• passive artifficially induced immunity

What is the difference of active and passive immunity?

active immunity is when antibodies are made by the individual, whereas passive immunity is when antibodies are recieved from another individual e.g through breast milk

Why is passive artificially induced immunity better for people with autoimmune diseases?

because it gives them immunity straight away as they have no B cells

How do vaccines work?

vaccines contain antigens from pathogens, stimulating a primary response when injected into the body → this means memory B cells and T cells are produced in case of a secondary infection

What do booster vaccines do?

they increase the number of antibodies and memory cells present

What type of vaccines do the diseases Influenza, Rubella and Tetanus use?

influenza - isolated antigens

rubella - live, weakened strains

tetanus - inactivated toxin called toxoid

What is herd immunity?

when a large population of people are vaccinated against a disease(s), meaning it is harder to maintain a chain of infection between people

What factors cause vaccinations to be successful?

• there must be few side effecrs so people aren’t discouraged

• staff must be skilled

• advanced equipment must be available for hygienic production, refridgerated storage and support

What are some disadvantages of vaccines?

• it is hard to vaccinate everyone

• people may be allergic

• free will is taken away of the vaccination was made an obligation

What is the components making up the structure of HIV?

• attachment proteins

• Reverse transcriptase molecule

• Protein capsid

• viral envolope

• RNA genome

• Matrix protein

What does the reverse transcriptase molecule do?

It’s an enzyme that converts RNA into DNA

What is the protein capsid formed from?

A phospholipid bilayer

What group of virus does HIV belong to and why?

Retrovirus group

This is because it uses RNA instead of DNA

Where does HIV replicate and why does it replicate here?

They replicate in T cells because the attachment proteins on HIV are complementary to receptors on T cells by chance

What does HIV do once entered the bloodstream?

1. A protein called CD4 on helper T cells binds to a protein on HIV

2. The protein capsid fuses with the cell membrane on the T cell and releases RNA into the T cell’s cytoplasm

3. The reverse transcriptase in HIV converts RNA to DNA which inserts into the T cell’s DNA

4. The HIV DNA uses the cell’s enzymes to produce messenger RNA which makes HIV particles

5. These HIV particles then break away from the helper T cell with a piece of its cell membrane around them, forming a lipid envelope

How does HIV cause the symptoms of AIDS?

• HIV destroys helper cells meaning B cells aren’t stimulated to produce antibodies and cytotoxic t cells aren’t stimulated to kil infected cells

• this means the person is susceptible to other infections and cancers

Why are antibiotics ineffective to viral diseases like AIDS?

• antibiotics work by preventing the formation of cell walls of bacteria

• since viruses have no cell structure, antibiotics cannot reach them as they have no attachment sites

What are monoclonal antibodies?

Antibodies that only bind to complementary abtigens

What is the ELISA test?

It can be used to detect HIV , it uses antibodies to detect the prescience and quantity of protein in a sample

How does the ELISA test work?

1. Have to immobilise the antigen/ antibody or it won’t work

2. Load well with patient’s blood plasma and leave it for some time

3. Wash to remove antibodies that haven’t binded to the antigen (vice versa)

4. Add the antibody from another organism to bind to ready binded antibody

5. Rinse again to remove any unbound enzyme-antibody complex to prevent false positive

6. Add coloured substrate to form enzyme substrate complex and colour change shows presence and quantity

What are monoclonal antibodies?

Antibodies that are identical to one another, originated from a clone of a single like of B cells