Biology - Immunity

What is an antigen

Foreign protein that triggers immune respone

What is an antibody

A protein specific to an antigen, released by B cells

Outline phagocytosis

• pathogen recognized by phagocyte because it’s foreign

• pathogen is engulfed by endocytosis

• vesicle fuses with pathogen, forming phagosome

• lysosome containing lysozyme fuses with it forming phagolysosome and enzyme hydrolyses pathogen and then it is releases via exocytosis

How does vaccination work?

• vaccine contains antigen from pathogen

• Macrophage presents antigen on its surface

• T helper cell with complementary receptor binds to antigen

• T helper cell stimulates B cells to undergo mitosis and secrete antibodies

Describe how B-lymphocytes respond when they are stimulated by antigens

• B lymphocyte engulfs antigen and becomes antigen presenting

• T helper cell with complementary receptor binds to antigen

• T helper cell stimulates B lymphocyte to undergo mitosis and make plasma cells which can secrete antibodies and memory cells which can differentiate into plasma cells and secrete antibodies

Suggest why it is advisable for people to be vaccinated against influenza every year

• Influenza mutates so its antigens change

• So influenza antibodies need replacing

Describe cell-meditated immunity

• T helper cell with complementary receptor binds to antigen on antigen presenting cell

• T cell clones by mitosis to:

• stimulate phagocytosis and mitosis of B cells, and activate cytotoxic T cells and become memory cells

How are monoclonal antibodies made ?

Why are they called monoclonal ?

• mouse injected with vaccine

• B cells are collected and fused with tumor cells

• forms hybridoma and then antibodies are collected

• Monoclonal → made from single group of identical B cells

Give two ways pathogens might cause disease when they enter the body

• release toxins

• damage / kill cells

Why are antibodies specific ?

It has specific primary structure meaning its tertiary structure is also specific so it is only complementary to one antigen

Describe the replication of HIV

• HIV’s attachment proteins bind to host helper T cell

• capsid is release and reverse transcriptase and RNA is released into it’s cytoplasm

• reverse transcriptase makes complementary DNA strand from RNA

• double stranded DNA is made and inserted into human’s DMA

What is herd immunity

Vaccinating a large amount of the population so most of the people are immune and the virus can’t spread

Difference between active and passive immunity

• Active is long term while passive is short term

• Active takes longer while passive is faster

• Active involves memory cells while passive doesn’t

• Active involves antibodies from plasma cells while passive involves antibodies from outside source