Immunology

Question 1

what happens when cells re-encounter an allergen?

Answer 1

allergen binds to IgE coated mast cells & basophils
degranulation
release of vasoactive mediators (histamine, tryptase)
increased expression of pro-inflammatory cytokines & luekotrienes

Question 2

name vasoactive mediators

Answer 2

histamine
tryptase

Question 3

which 2 cells express receptors that bind to the Fc region of IgE antibodies on their surface?

Answer 3

mast cells
basophils

Question 4

what happens in type 2a hypersensitivity?

Answer 4

destruction of antigen-positive cells via phagocytosis, opsonins (C3b)

Question 5

what happens in type 2b hypersensitivity?

Answer 5

stimulation of cell surface antigens,
complement mediated inflammation, C3a, C5a, MAC

Question 6

what activates macrophages to superkillers?

Answer 6

TH1

Question 7

what does TH2 do in autoimmunity?

Answer 7

IgE class switching
mast cell activation

Question 8

what is VDJ?

Answer 8

variable diverse joining
the random recombination of segmented genes to form unique VDJ sequence (for variable region of B cell)

Question 9

what is IPEX syndrome?

Answer 9

an X linked monogenic disorder

Question 10

what is IPEX caused by?

Answer 10

mutations in FOXP3 gene
causes failure of peripheral tolerance mechanisms due to absent regulatory (Treg) cells

Question 11

what can act as a superantigen? what is the process?

Answer 11

bacterial toxins
can non-specifically activate all T-lymphocytes, including auto-reactive T & B cells
Trigger T cell activation

Question 12

what is an epitope?

Answer 12

the part of an antigen that is recognised by the immune system and generates an immune response

Question 13

explain tissue injury and antigen sequestration?

Answer 13

previously sequestered (hidden) self-antigens can become exposed and cause an autoimmune reaction during infection/trauma
e.g. eyes, testes

Question 14

what stimulates immature tissue-resident dendritic cells to increase expression of co-stimulatory molecules?

Answer 14

TNF alpha

Question 15

what are possible defects in neutrophil cell cycle?

Answer 15

neutrophil development
trans-endothelial migration
neutrophil killing

Question 16

what is the mutation and its effect in SCN type 1?

Answer 16

(severe congenital neutropenia)
mutations in ELANE gene on chromosomes that encode for neutrophil elastase
accumulation of precursors in bone marrow i.e. neutrophils cannot mature

autosomal dominant

Question 17

what do you give to treat SCN type 1?

Answer 17

recombinant G0CSE
give recombinant cytokine, allows mature neutrophil production@ cannot mature properly if not enough ELANE precursor

Question 18

what is there an insufficiency of when there is defects in trans-endothelial migration?

Answer 18

ICAM-1
(an adhesion molecule)
insufficient adhesion molecules for neutrophils to move through

Question 19

what are the characteristics of leukocyte adhesion deficiency?

Answer 19

autosomal recessive
genetic defect in CD18 integrin gene
failure of neutrophil activation and migration

Question 20

what happens in granulomatous disease (CGD) ?

Answer 20

deficiency in intracellular killing mechanism: no respiratory burst
deficiency in p47phox gene- a component of NADPH oxidase complex
granuloma formation-starve of nutrients
cannot generate oxygen/ nitrogen free radicals

Question 21

what are treatments for PIDS?

Answer 21

immunoglobulin replacement therapy
aggressive infection management- oral/IV antibiotics & antifungals
definitive therapy- hematopoietic stem cell transplantation, gene therapy

Question 22

what is SCID?

Answer 22

severe combined immunodeficiency
it is failure of production of lymphocytes
i.e. T cells, B cells, NK cells

Question 23

what causes X-linked (the commonest form) of SCID?

Answer 23

mutation of a component of the IL-2 receptor

Question 24

what does the mutation in X-linked SCID cause?

Answer 24

(mutation is of component of IL-2 receptor)
inability to respond to cytokines
failure of T cell & NK cell development, immature B cell production
very low or absent T cells
normal/ increased B cells
poor developed lymphoid tissue & thymus

Question 25

what kind of infections lack functional T-cell compartments?

Answer 25

recurrent viral
recurrent bacterial
recurrent fungal

Question 26

what causes recurrent viral infection?

Answer 26

no CD8 cells
so no cytotoxic cells
no elimination of infection reservoir

Question 27

what causes recurrent bacterial infections?

Answer 27

CD4+T FH cells,
(co)stimulation of B cells, antibody production negatively affected

Question 28

what causes recurrent fungal infections?

Answer 28

faulty effector CD4+TH cells & antibodies
which are essential for defence against fungi

Question 29

what are possible pathways of SCID?

Answer 29

cytokine receptor deficiency
signalling molecule deficiency
metabolic defects
defective receptor arrangement

Question 30

treatments for SCID?

Answer 30

stem cell transplant from HLA identical sibling
stem cell transplant from other sibling/ parent/ from matched unrelated donor
IV Ig replacement
to avoid: no live attenuated vaccines

Question 31

what is Burton’s X-Linked hypogammaglobulinemia?

Answer 31

no circulating B cells
no plasma cells
no circulating antibody after first 6 months
BTK gene is essential for B cell development- not working

Question 32

what is a defence against intracellular mycobacteria?

Answer 32

IL-12 IFNgamma network