always rmb notes bio sac

physical barriers in animals

skin : Blocks pathogen entry

mucous membranes : Trap pathogens in nose, lungs, gut, etc.

chemical barriers in animals

Stomach acid: Kills ingested pathogens

Lysozyme (in tears/saliva) : Breaks down bacterial cell walls

microbiological barriers in animals

Normal flora (gut/skin bacteria) : Compete with pathogens for space & food

physical barriers in plants

Waxy cuticle : Prevents water loss + blocks pathogen entry

Cell walls : Tough structure to block pathogens

chemical barriers in plants

oxalic acid : distasteful to insects

Enzymes : (e.g. chitinase) Break down fungal cell walls

microbiological on plants

symbiotic bacteria - secrete toxins or outcompete w patho bacteria

what are allergens

• trigger allergic reaction

• non pathogenic

how is an immune system initiated

• immune cells recognize a pathogen, present its antigens, and activate T helper cells to start the immune response.

Why is the adaptive response specific?

targets one specific antigen with memory.

What is natural active immunity?

come from an infection, immune system makes memory cells

What is artificial active immunity?

vaccine is injected – body makes memory cells.

how does vaccine make antibodies

• safely exposes to dead/weakened version of pathogen

• b cells are activated and make antibodies

• some b cells become memory to rmb it

• if real pathogen is exposed ltr on, body rmbs and knows how to fight

what is vaccine

substance that protects you from disease

• contains a weakened/dead version of pathogen.

What is natural passive immunity?

occurs naturally, mother to baby (e.g. thru placenta or breast milk)

What is artificial passive immunity?

Injected antibodies – fast but temporary protection. (e.g. anti-venom injection)

humoral immunity

• work in extracellular environments (IN THE BODY FLUIDS)

• b cells cant enter cells as they are only found in body fluid/blood and destroy pathogens from the outside.

cell mediated immunity

• works in intracellular environments (IN THE CELL)

• some pathogens can hide among self cells

  ^ antibodies cant reach these pathogens bc antibodies found in blood/body fluid

cytotoxic T cells vs natural killer cells

• Tc cells and Nk cells both release perforin and granzymes (perforin = makes pores in cell mb, granzyme = enters through pores, releases enzymes that trigger apoptosis)

• Tc cells are part of the adaptive immune system, destory cells that present foreign antigen on mhc 1 (SPECIFIC)

• Nk cells are part of innate, destory cells that don’t have mhc 1 on the (NON SPECIFIC)

humoral immunity steps

1. Pathogen enters the body and is broken down into antigen fragments by APC

2. Antigen is displayed on the mhc 2 marker present on an apc 

3. Helper t cell binds to the antigen present on mhc 2 marker and becomes activated (releases cytokines)

4. T helper cell helps B cell with the same b cell receptors will bind to the antigen

5. after clonal selection, B cell undergoes clonal expansion 

6. B cell differentiates and makes Memory b cells and plasma b cells  

7. Antibodies will bind to pathogen and will cause functions of neutralisation, agglutination, opsonisation, complement activation, precipitation or etc 

cell mediated immunity pathway

1. Pathogen enters the body, breaks down into antigen fragments

2. antigen is presented on MHC 1 marker

3. cytotoxic t cell with matching receptor binds to antigen present on mhc 1, becomes activated. gets help from helper t cells releasing cytokines asw

4. activated cytotoxic t cells will expand to make more Tc cells or memory t cells

5. cytotoxic t cells leave lymph nodes, bind to infected body cell. WILL RELEASE PERFORIN AND GRANZYME TO DESTROY CELL

6. memory t cells retain info for future infectiosn

steps of an allergic reaction

• Allergen enters the body (e.g. pollen, peanuts).

• Immune system overreacts and makes IgE antibodies.

• IgE antibodies attach to mast cells.

• On second exposure, allergen sticks to the IgE on mast cells.

• Mast cells release histamine.

• Histamine causes symptoms like sneezing, swelling, runny nose, itching.

autoimmune disease

• immune system detects healthy cells as’nonself’ and triggers immune system to destroy and attac them in host tissue

why are booster vaccines good

• ensures good amount of memory cells are made to fight off infection

when is histamine released

• during inflammatory response

• released from mast cells

• cause vasodilation and increased vascular permeability (how easily small molecules can pass through blood vessel walls)

what is released during inflammatory response

• histamine from basophils and mast cells

• cytokines released by phagocytes (e.g. macrophages, neutrophils,etc)

• MONOCLONAL ABS used to inhibit cytokine signals + reduce inflammation

re-emerging pathogens

• infectious diseases that were once major health problem, declined, and rose again.

emerging pathogens

• new/rapidly increasing infection

• caused by new, mutated/re-emerging pathogens.

pandemics

• outbreaks of a disease that spread globally (world wide) within a short period of time

why do lymph nodes swell

•  lymphocytes become activated and proliferate. 

How b cells become activated

1. Antigen presented on the mhc 2 marker on an antigen presenting cell

2. T cell binds to this antigen, becomes activated and will release cytokines

3. Helper T cells will assist b cells (from cytokine release) to find the antigen complementary to their b cell receptors

4. B cells become activated from cytokine release

5. Activated b cells can then differentiate into plasma cells that secrete antibodies

Lymphatic system 

1. Lymphatic system transports b,t cells and apc’s to lymph nodes where immune responses can be initiated 

2. Lymph nodes act as sites where apc’s process and display antigens to activate b cells

3. Lymphatic system also helps distribute activated b cells and antibodies thru bloodstream

Memory B cells

• LONG LIVED

• rapidly differentiate into plasma cells that produce antibodies at a faster rate.

• this occurs so that the pathogen can be neutralised and then eliminated.

B and T cells

• Both mature in the primary lymphoid tissue

what do cytotoxic T cells target?

• target intracellular pathogens

• cytotoxic t cells only recognise antigens present on mhc 1 markers, which present intracellular self/non self antigens.