Lecture 11 Block 3

Question 1

what are the epitopes of antigens

Answer 1

recognition sites for B or T cells

Question 2

what is B cell and T cell specificity

Answer 2

antigen receptors on the surface of T or B cells recognize specific antigens/epitopes

Question 3

what is clone selection

Answer 3

an antigen interacts with lymphocytes that have corresponding antigen receptors and induces proliferation and differentiation of those lymphocytes

Question 4

what are the two types of clones that activated lymphocytes can develop into

Answer 4

short lived effector cells that combat the antigen and long-lived memory cells that memorize specific antigens

Question 5

what is self tolerance

Answer 5

As B and T cells develop, those that have antigen receptors against normal body cells are destroyed by apoptosis

Question 6

what is humoral immunity

Answer 6

the aspect of immunity that is mediated by macromolecules found in ECF such as secreted antibodies, complement proteins, and certain antimicrobial peptides. it defends against bacteria, toxins, and viruses in body fluids

Question 7

what is B cell mediated humoral immunity

Answer 7

B cell exposure to antigen tiggers clonal selection to produce memory B cells and plasma cells

Question 8

what are plasma cells and what do they do

Answer 8

secrete 2000 antibodies specific for antigen per second, they can circulate several weeks, binding to and marking antigen for destruction

Question 9

what are T dependent antigens (proteins)and what do they do

Answer 9

induce production of both plasma cells and memory B cells. it requires that helper T cells release cytokines in response to specific antigen.

Question 10

what do IL-2 and T-dependent antigens do

Answer 10

activate B cells to produce plasma cells and memory B cells

Question 11

what do T-dependent antigens (polysaccharides) do

Answer 11

activate B cells to produce plasma cells. T-dependnet antigens do not activate Helper T cells to release IL-2 , without helper T-cells releasing IL-2, proliferating B cells do not develop into memory B cells

Question 12

what are antibody functions

Answer 12

• neutralization
• agglutination
• opsonization
• complement activation
• enhancing activation of NK cells

Question 13

what does neutralization do

Answer 13

binding of antibody can block the activity of some pathogens

Question 14

what happens in agglutination

Answer 14

cross-binding of antibody and pathogen can link and clump pathogens together

Question 15

what happens in opsonization

Answer 15

binding of antibodies to a pathogen facilitates phagocytosis of the pathogen

Question 16

what happens in complement activation

Answer 16

IgM and IgG can activate complement system through the classic pathwat

Question 17

what happnens in enhancing activation of NK cells

Answer 17

IgG tails can bind to receptors on the surface of NK cells and allow NK cells to specifically attack antibody marked cells

Question 18

what is cell-mediated immunity

Answer 18

mediated by T cells and involved lysis of cells by cytotoxic T cells, it defends against bacteria and viruses in body cells

Question 19

what are the types of T lymphocytes

Answer 19

Helper T cells, cytotoxic T cells and suppressor T cells

Question 20

what do helper T cells do

Answer 20

secrete cytokines that enhance activity of B cells and other T cells

Question 21

what do cytotoxic T cells do

Answer 21

kill cells infected by virus or bacteria and other abnormal cells

Question 22

what do suppressor T cells do

Answer 22

secrete cytokines that suppress activity of B cells and other T cells

Question 23

what is the major histocompatibility complex

Answer 23

a set of cell surface proteins essential for the specific immune system to recognize foreign molecules

Question 24

what is antigen presentation

Answer 24

MHC binds antigen within the cell and transports it to the surface of the cell where it can be recognized by T cells

Question 25

what do Class I MHC cells do and where are they located

Answer 25

in all nucleated cells and present antigen to cytotoxic T cells

Question 26

what do class II MHC cells do and where are they located

Answer 26

in antigen presenting cells and present antigen to helper T cells

Question 27

explain helper T cell activation

Answer 27

• starts with binding of surface receptors on helper T cells with class I MHC foreign antigen complex on the surface of macrophages and B cells -the binding triggers IL-2 secretion by macrophages and B cells and IL-1 induced proliferation and differentiation of helper T cells
• helper T cells differentiate into secretory cells and memory cells
• Helper T cells secrete several cytokines to coordinate immune response

Question 28

what do secretory cells do

Answer 28

secrete cytokines that stimulate and regulate immune response

Question 29

what do memory cells do

Answer 29

produce stronger and quicker responses to subsequent infection with the same antigen

Question 30

explain cytotoxic T cell activation

Answer 30

• binding of surface receptors on cytotoxic T cells with class I MHC foreign antigen complex on the surface of infected cells or tumor cells
• this binding together with IL-2 released by activated helper T cells activate cytotoxic T cells
• activated cytotoxic T cells release performs to form pores in the membrane of infected cells and lyse the cells
• activated cytotoxic T cells secrete fragmenting which enter the infected cells through perforin induced pores and trigger apoptosis of the infected cells