40.1 Immune Deficiency

Question 1

What is the consequence of T-cell deficiencies?

Answer 1

Enhanced susceptibility to infections by viruses and facultative IV pathogens.

Question 2

Give examples of inherited T-cell deficiencies

Answer 2

*Thymic aplasia (lack of PLO –> unable to generate or mature thymocytes –> lack of T cells)
*Adenosine Deaminase (ADA) deficiency (deoxyadenosine accumulation –> prevention of DNA synthesis. S-adenosylhomocysteine build-up toxic to immature lymphocytes –> failure to mature)

Question 3

Give an example of an acquired T-cell deficiency

Answer 3

Loss of CD4+ T-cells due to HIV resulting in AIDS.

Question 4

What is the consequence of B-cell deficiencies?

Answer 4

Enhancement of susceptibility to pyogenic (S.pyogenes) infections

Question 5

What is an inherited B-cell deficiency?

Answer 5

Agammaglobulinemia (a group of inherited immune deficiencies characterized by a low concentration of antibodies in the blood due to the lack of particular lymphocytes in the blood and lymph)
*caused by KO of Btk enzyme preventing maturation of the cell via BCR signalling –> dramatic decrease in B-cell level.
*Greater strain on other aspects of innate immune system (e.g. neutrophils)

Question 6

What is the consequence of deficiencies of the innate immune system?

Answer 6

Enhancement of susceptibility to pyogenic infections.

Question 7

What are two types of innate immune system deficiencies?

Answer 7

• Cellular defects (e.g. involving PMNs - polymorphonuclear Leukocytes incl. neutrophils/ basophils etc)
• Deficiencies of secreted molecules (e.g. cytokines/ of a complement component)

Question 8

What is Chédiak-Higashi syndrome?

Answer 8

• A rare autosomal recessive disorder that arises from a mutation of a lysosomal trafficking regulator protein, which leads to a decrease in phagocytosis.
• The decrease in phagocytosis results in recurrent pyogenic infections, albinism, and peripheral neuropathy.

Question 9

What is Chronic granulomatous disease?

Answer 9

*Often caused by X-linked mutations to NOX (NADPH oxidase) used in ROS generation in neutrophils
*Neutrophils able to successfully ingest pathogens but unable to destroy once they have been internalised.
*Instead, neutrophils generate granulomata throughout the body to contain infected components.

Question 10

Name some possible treatments for immune deficiency.

Answer 10

• Replacement therapy e.g. give immunoglobins - (gives passive immunity. Often w/ prophylactic antibiotics to reduce risk of infection)
• Bone-marrow transplantation. (provide new, functional source of haematopoietic stem cells)
• Chemotherapy e.g. in AIDS.