1. Microbiology Chapter 16 Chapter 16 Immune System Disorders
The 3rd line of defense – The immune response is fantastic and helps us survive in a world populated by harmful agents – but sometimes things go wrong and our
own immune system causes us problems. Hay fever and food allergy are not uncommon. Severe disorders can be serious to fatal.
Hypersensitivity – body responds to allergen – immunological response – but tissue damage instead of immunity is the result.

2. 4. 4 types of reactions Microbiology Chapter 16
1. Allergen - antigen that causes a hypersensitivity reaction
2. Sensitized – person is exposed to this allergen
3. Hypersensitivity reaction – re-exposed to allergen – resulting in harmful reaction
4. 4 types of reactions

3. Fig. 16.1
Microbiology Chapter 16

4. Microbiology Chapter 16
Type 1 Hypersensitivity – Anaphylaxis (Pg. ___)
1. Occurs quickly 2 – 30 minutes
2. Involves IgE antibodies
3. Can be localized hypersensitivity or generalized
a. Localized common allergic reaction like hay fever, food allergies
b. Generalized – affect breathing, drop in blood pressure
4. Sensitizing results in production of IgE antibodies, 2nd exposure causes
IgE ab bind with surface of mast cells (in tissues) and basophils (blood)

5. Microbiology Chapter 16
a. Symptoms are related to these cells degranulating and dumping of chemical mediators like histamine
b. Histamine, most well known, causes vasodilation, edema, swelling, redness (common hay fever)
c. Other mediators can cause the symptoms of asthma
d. Systemic anaphylaxis – injected allergens in particular, drop in blood pressure (shock) can be fatal in minutes – insect stings, penicillin (hapten)

6. Fig. 16.3

7. Fig. 16.4

8. Microbiology Chapter 16
Type 2 Hypersensitivity – Cytotoxic reaction, IgM and IgG, these antibodies react
with cells, and with complement cause cells to lyse
1. Common transfusion reactions – pg.495 abo blood grouping
2. In transfusion reactions, ag-ab complex and complement in serum cause
donors rbc to lyse
3. Rh factor is also a cytotoxic reaction – Rh+ and Rh-, negative when
exposed to positive develops ab to rh ag, 2nd expsoure can result in
cytotoxic reaction

9. Microbiology Chapter 16
Type 2 Hypersensitivity – Cytotoxic reaction, IgM and IgG,
these antibodies react
with cells, and with complement cause cells to lyse
Common transfusion reactions – pg.___ abo blood grouping
2. In transfusion reactions, ag-ab complex and complement in
serum cause donors rbc to lyse
3. Rh factor is also a cytotoxic reaction – Rh+ and Rh-, negative when exposed to positive develops ab to rh ag, 2nd expsoure can result in cytotoxic reaction

10. Fig. 16.9

11. Microbiology Chapter 16
a. Erythroblastocysis fetalis – hemolytic disease of the newborn
b. Prevented now with rhogam – preformed antiRh antibody (passive immunity) prevents mom from developing own antibodies if exposed to Rh antigen at time of birth (P._____)
c. Total transfusion was used before

12. Fig

13. Fig

14. Fig

15. Microbiology Chapter 16
Type 3 – Immune complex hypersensitivity – antibodies against soluble antigens in the serum (pg.____)
IgG antibodies, the ab react with antigens in serum and these complexes are deposited in the cells of basement membrane tissue
2. The subsequent complement fixation results in severe tissue damage
3. Glomerulonephritis kidney damage
4. Systemic type 3 reactions – auto allergies – lupus (sle), rheumatoid arthritis (IgM and IgG complexes in tissue of joints)

16. Fig

17. Microbiology Chapter 16
Type 4 – Cell mediated hypersensitivity - t cells involved (td) – delayed hypersensitivity – symptoms are slow, at least a day or two
1. Time is required for the T cells and macrophages to migrate to site of foreign antigens
2. Allergic contact dermatitis is an example (poison ivy) see pg____
3. T cells are exposed to allergen, develop clone of t memory cells, these are circulating and are ready to interact with later exposure to antigen
4. Tb skin test uses this type of reaction to detect earlier exposure to tb ag
5. Inflammation reaction – macrophages dump (degranulate), (histamine reaction in tissue) redness, swelling, itch

18. Fig

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20. Microbiology Chapter 16
Autoimmune diseases – self antigens cause improper immune response, a break down in self tolerance (pg.____)
1. Body produces ab to own ag
2. Sensitized t cells react against the body’s own tissue antigens
Transplants – foreign tissue can be perceived as antigenic, a tissue can then be rejected as T cells and antibodies attack the foreign tissue – need immunosuppresant drugs

21. 1. Congenital – borne with defective immune system
Microbiology Chapter 16
1. Congenital – borne with defective immune system
2. Acquired – drugs, cancers, virus cause the degradation of immune system
3. HIV virus and aids – we’ll cover it later in disease of blood and emerging
diseases

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Microbiology Chapter 16