Allergy

Question 1

What is allergy:

Answer 1

The immune response becomes excessive and there is a response to harmless inocuous Ags

Question 2

Describe the 4 types of hypersensitivity:

Answer 2

I - IgE mediated
II - cytotoxic Abs against cell
III - Immune complex mediated
IV - Delayed time hypersensitivity

Question 3

What type of hypersensitivity are allergies?

Answer 3

Usually type I but also IV

Question 4

Describe type I:

Answer 4

Ag cross links IgE antibody held on surface of mast cells or basophils by high affinity FCER receptor
Release granules containing inflammatory mediators like histamine

Question 5

Why do we overproduce IgE -what is it called?

Answer 5

Atropy
associated with IL4 and IL13 production by Th2 cells which cause B cells to class switch to IgE

Question 6

Reasons for type I hypersensitivity:

Answer 6

Genetic

Disruption of mucousal or skin barriers cuz pollution or infection

Question 7

Treatments for type I hypersens:

Answer 7

Avoid allergens but drugs always available

Question 8

Drugs for type I hypersensitivity:

Answer 8

Crolomyn sodium prevents release of histamine

Antihistamines prevent its action

Question 9

Example of type II hypersensitivity:

Answer 9

haemolytic disease of the newborn

Question 10

Describe haemolytic disease of new borns:

Answer 10

Mom is RhD - and baby is RhD+ there isn’t a problem in the first pregnancy but at birth, mom becomes sentisised to the foreign RhD+ antigens and makes antibodies
this during a subseq pregnancy will cross the placenta and damage fetal erythrocytes

Question 11

What to do with RhD- moms:

Answer 11

Inject them with preformed antibodies and RhD before first birth so infants RhD+ erythrocytes fail to stimulate moms B cells

Question 12

Where is type III seen:

Answer 12

In SLE

Question 13

Type IV how?

Answer 13

Involves expansion of T cells