Cell Recognition + Immune System

Name the 4 pathogens and what they do

1. Bacteria - produce toxins

2. Virus - burst and destroy cells

3. Protoctist - take over and break cells

4. Fungi - digest cells

Describe the physical and chemical barriers

• Skin - produces sebum and acts as barrier

• Mucus - traps pathogens in ears, nose, throat

• Expulsion - coughing, sneezing, vomiting, diarrhoea

• Blood Clot - platelets prevent entry

Immune system recognizes antigens from…

pathogens, abnormal cells, foreign cells, toxins

Describe the process of phagocytosis

• Pathogen attracts phagocyte

• Antigen recognised as non-self and engulfed

• Phagosome formed which fuses with lysosome to form phagolysosome

• Hydrolytic enzymes (lysozymes) digest and destroy pathogen

• Antigen-presenting cell formed (APC)

Name and describe the 2 lymphocytes

• T cells - mature in thymus gland (helper, cytotoxic and memory)

• B cells - mature in bone marrow

Describe the process of cell-mediated immunity

• Helper T cells binds to complementary antigen on APC

• Helper T cell is activated and divides by mitosis

• Cloned cells differentiate and fulfill different functions

What are the 4 functions of cloned helper T cells

• Memory T cells - long term immunity

• Phagocytosis - engulf pathogens

• B cells - produce antibodies

• Cytotoxic T cells - produce perforin to cause cell death

Describe the process of humoral response

• B cell binds to complementary antigen

• B cell engulfs pathogen to become APC

• Clonal selection - Helper T cell binds to and activates B cell

• Clonal expansion - B cell divides by mitosis to form plasma and memory cells

• Plasma cells secrete specific pathogens

Describe the structure of an antibody

a Y-shaped glycoprotein made from 2 heavy polypeptide chains and 2 light polypeptide chains held together by disulphide bridges

Name the 3 roles of antibodies

1. Agglutination of pathogens (clumping together to make phagocytosis easier)

2. Neutralisation of toxins

3. Preventing pathogens from binding (blocking cell-surface receptors)

Name the uses of monoclonal antibodies

• Diagnosing and treating disease

• Pregnancy tests

• Cancer detection

What is the ELISA test

Enzyme-linked ImmunoSorbant Assay

• direct uses 1 antibody

• indirect uses 2 antibodies

Describe active immunity

Immune system makes its own antibodies

• Natural - body is infected

• Artificial - body is vaccinated

Describe passive immunity

Body receives antibodies from elsewhere

• Natural - mother to baby

• Artificial - injected antibodies

Features of a successful vaccine

• available and affordable

• minimal side effects

• storage and transport

• herd immunity

Vaccines may be unsuccessful due to…

• people with weak immune systems

• antigenic variability

• other varieties of same pathogen e.g the cold

• ethical or religious issues

Describe HIV structure

Human immunodeficiency virus

• Genetic material and reverse transcriptase enzyme surrounded by capsid with envelope and attachment proteins surrounding

Describe the process of HIV replication

• Attachment proteins attach to helper T cell receptors

• Reverse transcriptase converts viral RNA into DNA

• Viral DNA inserted into cells genome and translated to make viral proteins to make new HIV viruses

What is AIDS

Acquired immunodeficiency syndrome

• can lead to increased chances of infection and death

• antiretroviral drugs decrease symptoms