when the immune system goes wrong

Question 1

what is atopy

Answer 1

inherited tendency to make immediate hypersensitivity responses (30-50% of the population has this)

Question 2

what happens in allergies

Answer 2

APC presents allergen to cd4-> cd4 differentiates into Th2 (triggered by IL4)->  il2,4,5,13 released-> b cells proliferate-> class switch to IgE and differentiate into plasma cell
IgE binds to allergen-> mast cell degranulates-> histamine release

Question 3

Allergy-related diseases and treatments

Answer 3

Asthma
Perennial rhinitis 
Eczema 
Anaphylaxis 
Treatments: antihistamines/beta-2 adrenoreceptor agonist/corticosteroids/desensitisation/monoclonal antibody

Question 4

What class are serum autoantibodies ? What are they used for ?

Answer 4

IgG
Monitor disease activity
Diagnostic tools
Predict future disease

Question 5

Proof of autoimmunity

Answer 5

Transfer of disease by immune effectors into reciepient without disease eg placental transfer of antibodies

Clinical responsiveness to immune suppression

Question 6

Graves’ disease

Answer 6

Usually, pituitary gland produces TSH-> thyroid produces thyroxine-> negative feedback by thyroxine prevents further TSH production
In Graves’ disease, igG autoantibodies bind to TSH receptor-> thyroid gland keeps making thyroxine in an unregulated manner -> hyperthyroidism

Question 7

Myasthenia Gravis

Answer 7

Pt develops antibodies against ach receptor-> ach receptors at effector is damaged-> less ach receptors-> insufficient engagement between ach and ach receptors-> no/poor muscle contraction-> muscle weakness and fatigue

Question 8

Why is type 1 diabetes T cell mediated

Answer 8

Treg fails to suppress
CD8 T cells kill beta-cells
APC presents beta-cell antigens to CD4 T cells -> differentiation into
Th1-> macrophage activation/CD8 proliferation
Th17-> epithelium and fibroblasts secrete antimicrobials/neutrophil attraction
Th2-> B cell div/class switching/plasma cell differentiation/affinity maturation/eosinophil activation

Question 9

Primary vs secondary immunodeficiencies

Answer 9

Primary: inherited
Secondary: acquired

Question 10

Examples of primary Immune deficiencies

Answer 10

Chronic granulomatous disease: neutrophils surround area of infection but no antimicrobial properties-> granuloma formation
SCID(secrete combined immune deficiency): no B and T cells
Di George syndrome: no thymus-> no T cells
Hypergammaglobulinemia: defect in gene encoding CD40 ligand-> Tcells and B cells cant interact-> plasma cells don’t develop, no class switch-> only igM made

Question 11

What happens in AIDSD

Answer 11

Virus infects CD4 cells-> CD4 count falls-> CD8 increases to bring infection under control (to an extent)-> infected CD4 cells fall further

Question 12

What are iatrogenic immune deficiencies? 2 examples

Answer 12

Immune based therapies-> secondary immune abnormalities
Eg monoclonal anti-TNFalpha therapy for rheumatoid arthritis-> opportunistic infections including mycobacterial infections
Eg monoclonal anti-IL17 therapy for psoriasis-> fungal infections

Question 13

Why is there failure of immune surveillance in cancer? Treatment

Answer 13

PDL1 on cancer cell (Programmed death ligand-1) engages PD1-> T cell inactivated-> immune response evaded
Antibody to PD1 OR PDL1