Immunodeficiencies

Question 1

Primary immunodeficiency

Answer 1

Results from genetic or developmental defect in immune system

Question 2

Secondary immunodeficiency

Answer 2

Acquired as a result of other disease or condition (malnutrition, drug treatments, etc.)
Can be reversed

Question 3

What branches of immune system can primary immunodeficiencies affect??

Answer 3

Adaptive (T and/or B cells)

Innate (phagocytes, complement)

Question 4

Consequences of primary immunodeficiencies depends on what two factors?

Answer 4

Number of immune system components involved

Type of immune system components involved

Question 5

Defects occurring at what period during hematopoietic development affect the entire immune system?

Answer 5

Early stages of hematopoietic developmental scheme

Question 6

Defects in more highly differentiated components of immune system have what kinds of consequences?

Answer 6

More specific, less severe

Question 7

Deficiencies in humoral immunity leave patients susceptible to what kinds of infections?

Answer 7

Extracellular bacterial infections

Question 8

X-linked agammaglobulinemia

Answer 8

Deficiency in humoral immunity
Caused by defect in B cell maturation and VDJ rearrangement
Low levels of mature B cells and antibodies

Question 9

Transient immunodeficiency

Answer 9

Babies are born with low levels of IgG- production doesn’t begin until about 6 months of age
IgG levels are low around 6 months- maternal antibodies wear off, IgG is just starting to be made

Question 10

Hyper IgM syndrome

Answer 10

Humoral immune deficiency
Defect in class switching: T helper cells don't express CD40 (co-stimulatory molecule needed for B cell activation)
Recurrent, chronic bacterial infections

Question 11

Selective IgA deficiency

Answer 11

Humoral immune deficiency
Decreased IgA, but normal IgG and IgM
Defect in differentiation of B cells to plasma cells
Patients are generally asymptomatic, but some have a higher incidence of respiratory and GI infections

Question 12

Deficiencies in cell-mediated immunity would lead to an increased susceptibility to what kinds of infections?

Answer 12

Viral, protozoan, fungal

Question 13

How are cell-mediated immunodeficiencies diagnosed?

Answer 13

Decreased T cell numbers
Decreased proliferative responses of T cells
Deficient delayed-type hypersensitivity response

Question 14

DiGeorge syndrome

Answer 14

Cell mediated immunodeficiency
Lack of T cell maturation
Susceptible to viral and bacterial infections
Heart disease, behavioral problems, etc.

Question 15

Severe combined immunodeficiency syndrome

Answer 15

Cell mediated immunodeficiency
Defects in T and B cell production
Susceptible to any infection (bubble boy)

Question 16

Most common cause of severe combined immunodeficiency syndrome

Answer 16

Recombination activating genes (RAG 1 and 2) are defective: no synthesis of T or B cell receptors

Question 17

Phagocytic deficiencies result in susceptibility to what types of infections?

Answer 17

Bacterial, fungal

Question 18

Leukocyte-adhesion deficiency

Answer 18

Phagocytic deficiency
Defect of integrin adhesion molecules: neutrophils can’t get into tissues
Susceptible to bacterial infections

Question 19

Chronic granulomatous disease

Answer 19

Phagocytic deficiency
Defect in intracellular killing of ingested bacteria (decreased hydrogen peroxide by cytochrome b): bacteria are carried to organs by phagocytes, where they give rise to lesions
Patients with this disease die in childhood due to septicemia

Question 20

Most common immunodeficiencies occur at what two points in life cycle?

Answer 20

Young

Old

Question 21

Treatments for immunodeficiency

Answer 21

Replacement of missing protein (e.g. antibodies)
Replacement of missing cell type or lineage (bone marrow, etc.)
Gene therapy

Question 22

Most common cause of secondary immunodeficiency

Answer 22

Malnutrition

Question 23

Ways that HIV can be transmitted

Answer 23

Sexual contact
Pregnancy, childbirth, breast feeding
Injection drug use
Occupational exposure
Blood transfusion/organ transplant

Question 24

How HIV affects the immune system

Answer 24

Attacks CD4 T cells: uses them to replicate, then destroys them
Without T helper cells, body becomes unable to fight infections: AIDS

Question 25

HIV treatment targets

Answer 25

Chemokine receptor antagonists (prevent HIV binding to cell)
Inhibit viral fusion (virus entering cell)
Inhibit reverse transcription (viral RNA made into DNA)
Inhibit integrase (enables integration of DNA into cellular genome)
Inhibit protease (cleavage of viral proteins that can then be assembled)

Question 26

Why HIV vaccines can’t be made

Answer 26

HIV infection can remain latent for long periods
HIV mutates at a rapid pace
Killed HIV doesn’t retain antigenicity and live vaccine raises safety issues