Topic 2-The immune response Flashcards
What are the 4 stages of the immune response?
-Phagocytosis
-T cells
-B cells
-Antibody production
What is a phagocyte?
-A type of white blood cell that carries out phagocytosis
Where are phagocytes found?
-Found in the blood and tissues
True/ false: Phagocytes are the first cells to respond to an immune system trigger inside the body
True
What is the first step of phagocytosis?
-A phagocyte recognises the foreign antigens on pathogen
What is the 2nd step of phagocytosis?
-The cytoplasm of the phagocyte moves around the pathogen, engulfing it
What is the 3rd step of phagocytosis?
-The pathogen is now contained in a phagocytic vacuole in the cytoplasm of the phagocyte
What is the 4th step of phagocytosis?
-A lysosome fuses with the phagocytic vacuole
-The lysosomes break down the pathogen
What is the 5th step of phagocytosis?
-The phagocyte then presents the pathogen’s antigens
-It sticks the antigens on its surface to activate other immune system cells
-The phagocyte is acting as an antigen-presenting cell
What does the T cell stand for?
-T-lymphocyte
What is a T cell?
-A type of white blood cell
What activates the T cell?
-It has receptor proteins which bind to complementary antigens presented by phagocytes
How do helper T cells respond?
-Release chemical signals which activate and stimulate phagocytes
-Activate B cells
How do cytotoxic T cells respond?
-Kill abnormal and foreign cells
What are B cells?
-B lymphocytes
-A type of white blood cell
What do B cells form and how?
-Antigen-antibody complex
-They are covered in antibodies
Define antibodies
-Proteins that bind to antigens to form an antigen-antibody complex
What is different about each B cell?
-They have a differently shaped antibody on their membrane
Explain the process of clonal selection
-Antibody on the surface of B cell meets complementary antigens they bind together
-With substances released from helper T cells it activates the B cell
What do activated B cells divide into?
-Plasma cells
Why do antibodies bind to antigens?
They have a complementary shape
What do B cells and T helper cells have in common?
-Both have receptor proteins
-On B cells they bind to the signalling molecules released by the T helper cells
What is the function of plasma cells?
-They secrete loads of antibodies specific to the antigens
(monoclonal antibodies)
How many binding sites does an antibody have?
-2
-So they can bind two pathogens at a time
What is agglutination?
When pathogens clump together
What happens after agglutination? What does this lead to?
-Phagocytes then bind the antibodies and phagocytose many pathogens at a time
-The destruction of pathogen carrying the antigen in the body
What does the specificity of an antibody depend on?
-Variable regions which form the antigen binding sites
Why does each antibody have a variable region with a unique tertiary structure that is complementary to one specific antigen?
-Different amino acid sequences
What is the same in all antibodies?
-The constant regions
What are the 2 parts of the immune response?
-Humoral
-Cellular
What makes up the cellular response?
-The T cells
-Other immune system cells they interact with (phagocytes)
What makes up the humoral response?
-B cells
-Clonal selection
-Production of monoclonal antibodies
What is the primary response?
When an antigen enters the body for the first time and activates the immune response
Why is the primary response slow?
There aren’t many B cells that can make the antibody needed to bind to the antigen
What will happen when the person is producing the antibodies?
They will show symptoms
What happens after both the B and T cells are exposed to the antigen?
Memory cells are created
What is the function of memory T cells?
-Remember the specific antigen and will recognise it the 2nd time around
What is the function of memory B cells?
-Record the specific antibodies needed to bind to the antigen
What is meant by immune?
-Their immune system can respond to the 2nd infection
What is the secondary response?
-When the same pathogen enters the body again, the immune system will produce a quicker, stronger immune response
What happens during the secondary response?
-Clonal selection happens more quickly
-Memory B cells activated- divide into plasma cells that produce the right antibody for antigen
-Memory T cells are activated and divide into the correct T cell to kill the cell carrying the antigen
Are symptoms shown during the secondary response?
-No
