W4.3

Question 1

Natural killer cells characteristics

Answer 1

”- lymphocytes that do not express the markers of either T or B cells

• 5-10 % of the circulating lymphoid pool found mainly in the spleen and peripheral blood
• have the ability to mediate cytolytic reactions and kill target cells without prior exposure to them
• large producer of INFy
• involved early in infection (activated by IFNs and IL-12)
• this gives time for the acquired response of specific T and B cells to be activated “

Question 2

similarities and differences of NK vs T cells

Answer 2

”- Share a preogenitor with T cells and share some ““T cell”” surface markers

• dont develop in the thymus
• dont rearrange genes
• kill in similar fashion as CTLs (FasL and contain perforin and granzyme granules) “

Question 3

NK cells activity and stimulation

Answer 3

"Activity - based on balance of inhibitory and activatory signals 
Stimulated - exposure to cytokines such as interleukin-12, interferon gamma, and interferon beta
- inhibitory signal is based on recognition of MHC class 1 protein, expressed on all healthy self cells "

Question 4

How NK cells are triggered

Answer 4

”- diseased and cancerous cells tend to lose their ability to produce MHC proteins

• NK cells are triggered by a lack of MHC antigens, sometimes reffered to as recognition of ““missing self””
• if an inhibitory signal is not received at the same time as the ““activation”” signal, then NK cells release perforins and granzymes “

Question 5

preventing NK killing

Answer 5

”- NK cells express inhibitory receptors (KIR)

- MHC 1 interacting with KIR is a potnt inhibitory signal “

Question 6

ADCC

Answer 6

antibody-dependent cell cytotoxicity

Question 7

each B cell expresses

Answer 7

“a unique - antigen binding receptor on its membrane
BCR = membrane bound antibody
- maturation includes complex gene rearrangements that produce a diverse range of antibody binding options (1/cell) “

Question 8

Humoral Immunity

Answer 8

”- comprised of antibodies found in all extracellular fluids that are secreted from specialized B cells (plasma cells)
- principal defense against microbes and toxins (anything extracellular) “

Question 9

B cell Receptor/Antibody function

Answer 9

“1 - immune complex
2 - immune complex/ pathogen
3 - target cell / pathogen
4 - antigen “

Question 10

B cell receptor/activation

Answer 10

• Bcell receptors can recognize proteins in their native or denatures conformations, simple chemical groups, lipids, carbohydrates, and nucleic acids

Question 11

B cell activation

Answer 11

“the surface of a B cell is covered in identical BCRs, several of these receptors must be bound at the same time to induce activation.
ACTIVATION THRESHOLD
the concentration of an antigen greatly influcences the initiation of an immune response and also acts as a control on it “

Question 12

T cell dependent antigens

Answer 12

usually protein, can stimulate production of all 5 classes of antibodies and can ilicit a secondary/booster response

Question 13

T cell independent antigens

Answer 13

antigens that have a large repetitive structure that can induce a small amount of IgM production, without T cell help (LPS, Flagellin)

Question 14

How T cells help B cell acitvation

Answer 14

”- B cells need help from T cells to do anything beyond recognize the antigen
- T cell help can be T-B cell contact or secretion of cytokines needed to activate the B cell