Lecture 7-antibodies to infection

Question 1

How do foreign antigens meet the immune system in the skin

Answer 1

antigen uptake by Langerhan;s cells in skin.
Langerhan’s cells leave the skin and enter the lymphatic system.
Langerhans cells enter the lymph node to become dendritic cells presenting the engine on their surface.
T cells then cluster around them and those with receptors specific for the antigen become stimulated.

Question 2

In the secondary lymphoid organs the antigens are presented to lymphocytes by

Answer 2

specialised APC using MHC structures on their surface which hold fragments of antigen and present them to specific receptors on lymphocytes.

Question 3

Lymphocyte effectors

Answer 3

B cells- antibody production

CD8 cells- antigen specific cytotoxicity

Question 4

lymphocyte regulators

Answer 4

CD4 cells-Cytokine production, helper T cells, Regulatory cells

Question 5

three ways of shape recognition

Answer 5

some characteristic common to many substances eg. bacterial wall sugars.
recognition of some unique characteristic of a particular foreign substance eg. viral capsid protein.
recognition of something common but in an uncommon context eg. myocardium shapes on streptococcal bacteria- hence why heart muscle is damaged in some people.

Question 6

primary response

Answer 6

animal responds to an antigen that is has not previously encountered. usually a lag period of a few days before antibodies which are specific for that antigen appear in the blood. antibodies do not last forever and in the absence of antigen the primary response gradually decays

Question 7

secondary response

Answer 7

animal is exposed to the same antigen later in life it responds much more rapidly and more vigorously. immune system had remembered the primary rencounter with the antigen and adapted its resources to respond more effectively to subsequent encounters.

Question 8

B cells and the generation of antibody responses

Answer 8

antigens bind to the surface immunoglobulin (sIg) receptors on antigen-sensitive B cells in secondary lymphoid organs that have receptors with high affinity to bind enough antigen to overcome their activation threshold.
further activation signals are delivered to the activated b cells by a co operating system consisting principly of helper t cells.
activation of antigen sensitive b cells results in proliferation to form a population of plasma cells which secrete antibodies of the same antigen binding specificity as was present on the sIg of their precursor B cell and memory b cells for secondary responses.

Question 9

4 ways antibodies work within the body

Answer 9

direct neutralisation-antiviral antibodies prevent virus absorption
opsonisation-phagocytic cells through cell surface receptors for Fr and C3b can bind with high affinity to antibody coated foreign material or material to which C3b has adhered following complement activation
antibody dependent cell mediated cytotoxicity-K cells have Fc receptors and C3b receptors on their surface. K cells are not phagocytic but instead are able to kill cellular material by delivering short rang cytotoxicity
complement activation-

Question 10

chemotaxis

Answer 10

attraction of phagocytic cells to the site of complement activation

Question 11

lysis

Answer 11

destruction of cell membranes (of bacteria for example) to which the antibodies that activated the compliment cascade are attached