Humoral Response

Question 1

How is humoral response activated

Answer 1

Macrophages become APC by combining MHC complex with pathogen antigen and move to surface. APC then binds to T helper cell with correct receptor in clonal selection and T helper cell activated

Question 2

What happens when T helper cell activated

Answer 2

Undergoes clonal expansion which increases number of T helper cells as divide by mitosis and T memory cells

Question 3

How are B cells activated

Answer 3

APC binds to B cell and T helper produce cytokines which activate B cell

Question 4

What happens when B cells activated

Answer 4

Undergoes clonal expansion to produce plasma cells(B effector cells which produce antibodies complementary to antigens on pathogen) and B memory cells(remain in blood for long time and remember antibodies needed)

Question 5

What are the three roles of antibodies

Answer 5

-neutralise toxins released by bacteria, toxin-antibody complex also phagocytosed
-agglutinating pathogens causing pathogens to clump together so can be phagocytosed all together
-binding to antigens on surface of pathogen and blocks these meaning cannot bind to host cells and marks pathogens for phagocytes to destroy

Question 6

Role of plasma cells and what are they

Answer 6

Clone of B cells and secrete many antibodies specific to the antigen into the blood which will bind to antigens on surface of pathogen to form many antigen-antibody complexes

Question 7

Structure of an antibody

Answer 7

-four polypeptide chains, 2 heavy and 2 light with each chain having a variable and a constant region
-variable regions form antigen binding sites, shape is complementary to a particular antigen and these regions differ between antibodies
-hinge region- allows flexibility when antibody binds to antigen
-constant regions allow binding to receptors on immune cells eg phagocytes and is same in all antibodies

Question 8

What type of bond hold the polypeptide chains together in an antibody

Answer 8

Disulfide bridges

Question 9

What are the two types of antibodies and differences in their structure

Answer 9

Can be membrane bound (attached to the membrane of a B cell) or can be secreted (free from any attachment)
-have slightly dif heavy chain proteins because membrane bound antibodies have an extra section of protein that anchors them to the B cell membrane, secreted don’t need this

Question 10

How many genes code for both heavy chain proteins in antibodies

Answer 10

Single gene which is copied into mRNA which can be modified before it’s translated into protein