Adaptive immune system

Question 1

lymphocyte repertoire

Answer 1

Range of receptors able to recognise foreign antigens

Question 2

what creates the diversity of recognition receptors (TCRs) and antibodies?

Answer 2

gene recombination

Question 3

advantages of diverse TCRs and antibodies

Answer 3

able to determine self vs non-self

able to change, develop and adapt

Question 4

types of T cells

Answer 4

TH = helper cells

TC = cytotoxic cells

Treg = regulatory cells

Question 5

where to B cells mature?

Answer 5

bone marrow

Question 6

where do T cells mature?

Answer 6

thymus

Question 7

humoral immunity

Answer 7

B cells

Question 8

cell-mediated immunity

Answer 8

T cells

Question 9

antigen presenting cells

Answer 9

Specialised cells which capture microbes + other foreign antigens

present to lymphocytes with other co-stimulatory signals

Question 10

APCs

Answer 10

MAIN = dendritic cells in epithelia and most organs

-> take up antigen, process it + carry it to T cells in lymph nodes

OTHERS = macrophages, neutrophils and B cells

Question 11

where do lymphocytes originate?

Answer 11

bone marrow

=> derive from haemopoietic stem cells

Question 12

what occurs at primary lymphoid organs?

Answer 12

T cells migrate to thymus to mature and undergo selection

Question 13

what occurs at secondary lymphoid organs?

Answer 13

mature/naive cells leave primary lymphoid organs + enter circulation to reach lymph nodes

effector cells migrate out into tissues and return through lymphatics

Question 14

where do antigens enter?

Answer 14

through epithelia and are carried in lymphatics to nodes

Question 15

where do blood-bourne antigens enter?

Answer 15

via spleen

Question 16

role of T cells

Answer 16

Cell mediated cytotoxicity (Tc)

Activation macrophages (phagocytosis)

Recruitment of neutrophils

Question 17

role of B cells

Answer 17

Antibody production (phagocytosis)

Question 18

role of cytokines

Answer 18

[Il-2,4,5,13, IFN(gamma), TGF(beta), Lymphotoxin -TNF(beta)]

All produced by T cells

Most activate other cells

Stimulate antibody production

TGF(beta) = inhibitory

Question 19

homeostasis of adaptive immune response

Answer 19

Return to resting state after elimination of antigen

Involves apoptosis of excess cells

Survival of memory cells

Persistence of antigen can result in prolonged activation => chronic inflammation + autoimmunity

Question 20

what happens to B cells after activation?

Answer 20

become antibody-secreting plasma cells

Question 21

what happens to some B cells after infection?

Answer 21

survive as memory cells

Question 22

MoA of B cells during infection

Answer 22

1. endocytosis of microbial protein antigen via B cell -> receptor mediated
2. antigen processing and presentation

3.Ig(alpha) and Ig(beta) associates with B cell receptor and antigen => transduces signal

4. class II MHC-protein complex
5. T-cell recognition of antigen

Question 23

MoA of T cells during infection

Answer 23

1. antigen presentation to TH cells
2. activation
   -> expresion of CD40 ligand
   -> cytokine secretion (Il-4)
3. activation of B cell by cytokine + CD40 ligand
4. B cell proliferation and differentation

Question 24

innate vs adaptive immunity

Answer 24

[innate - first 12hrs]

-epithelial barrier
-phagocytes
-complement
-NK cells

[adaptive - up to 5 days]

-B lymphocytes -> antibodies
-T lymphocytes

Question 25

how is B-cell activation down-regulated?

Answer 25

via engagement of Fc co-receptor