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micr 386 > module 09 section 03 (immunodeficiency) > Flashcards

module 09 section 03 (immunodeficiency) Flashcards

1
Q

recall: what are immunodeficiency diseases?

A

a defect in the immune system such that the body cannot effectively fight infections or prevent diseases

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2
Q

recall: what are the two main categories of immune disorders?

A

(1) 1° imunideficiency: inherited immunodeficiencies

(2) 2° (acquired) immunodeficiency: a result of environmental factors that compromise the immune system

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3
Q

more specifically, what is 1° immunodeficiency caused by?

A

hereditary or genetic defects that result in tha absence or improper functioning of parts of the body’s immune system

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4
Q

all 1° immunodeficiency disease share what common feature?

A

causing a defect in one of the body’s immune system functions, by affecting either one or multiple components

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5
Q

generally, how are 1° immunodeficiency diseases classified?

A

based on which part of the immune system is affected

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6
Q

what are the 5 major classifications of 1° immunodeficiency disease?

A

(1) humoral immunity (B-cells)
(2) cellular immunity (T-cells)
(3) humoral and cellular immunity (B-cells and T-cells)
(4) phagocytes
(5) complement proteins

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7
Q

with 1° immunodeficiencies, the affected component of the immune system can be:

A

missing, reduced in number, or abnormal and malfunctioning

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8
Q

what classification of accounts for more than half of 1° immunodeficiencies?

A

those involving problems with B-cells

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9
Q

what is DiGeorge syndrome?

A

1° immunodeficiency that results from a depletion of a segment of chromosome 22

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10
Q

DiGeorge syndrome causes developmental ______ in which the ______?

A
  • thymic aplasia

- thymus fails to develop

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11
Q

what does developmental thymic aplasia result in?

A

the absence of cell-mediated immunity due to the absennce of differentiated/mature T-cells (T-cells mature in the thymus)

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12
Q

the absence of cell-mediated immunity is aka?

A

anergy - absence of the normal immune response to a particular antigen or allergen

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13
Q

patients with DiGeorge syndrome have an increased susceptibility to?

A

fungal and viral infections

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14
Q

what is Bruton’s (X-linked) agammaglobulinemia?

aka XLA

A

inherited immunodeficiency disease caused by mutations in the gene encoding for Bruton tyrosine kinase

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15
Q

what is BTK (bruton tyrosin kinase) responsible for?

what are the implications of this for Bruton’s agammaglobulinemia?

A
  • mediating B-cell development from pre B-cells to mature B-cells through a signalling effect on the B-cell receptor
  • individuals with bruton’s agammaglobulinemia do not generate mature B-cells
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16
Q

what is implied by the lack of mature B-cells in Bruton’s agammaglobulinemia?

A

lack of Igs in the bloodstream

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17
Q

the deficient humoral immune response in individuals with

Bruton’s agammaglobulinemia makes them more prone to what?

A

serious and fatal bacterial infections

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18
Q

Bruton’s agammaglobulinemia presents clincially similar to what other disease?

A

hypogammaglobulinemia (CVID), however CVID is not an inherited disorder with known genetic causes

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19
Q

how is XLA typically treated?

is this a cure?

A
  • by intravenous infusion of antibodies

- does not cure but reduces severity of infections due to passive immunity from the exogenous antibodies

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20
Q

historically, XLA was mistaken for what disease?

is this more severe or less severe than XLA?

A

severe combined immunodeficiency (SCID) - more severe

21
Q

what is SCID?

A
  • a group of defects from one of many genes that results in a heterogeneous disorder
  • it causes a defective antibody response either directly through mature B-cell malfunctioning or indirectly through ineffective T-cell dependent B-cell activation
22
Q

what is the role of the genes associated with SCID?

A

proper development of B-cells and T-cells

23
Q

SCID causes a defective antibody response _____ through _____ or _____ through _____?

A
  • directly through mature B-cell malfunctioning

- indirectly through ineffective T-cell dependent B-cell activation

24
Q

SCID makes affected individuals highly susceptible to what?

A

life-threatening infections by viruses, bacteria and fungi

25
Q

SCID is also known as what? why?

A

“bubble boy” disease - affected individuals must live in sterile environments due to their vulnerability to infectious diseases

26
Q

are most SCID cases X-linked? if so why, if not what are they?

A

yes - due to mutations in the gene that encodes for the common gamma chain found on the X-chromosome

27
Q

mutations in the SCID gene prevent? due to what?

why?

A

the development of a fully functional immune system due to:

  • low T-cell and NK counts
  • non-functional B-cells
  • becuase gamma is a characteristic of receptors for IL-2, IL-4, IL-7, IL-9 and IL-15, which are implicated in the development of B and T cells
  • if there’s a mutation in this receptor, these cytokines are non-functional and cannot exert their effects in B/T-cell development
28
Q

what therapeutic modality has potential for treating patients with SCID? why?

A

gene therapy - because these conditons are caused by defects in an identifiable molecule with a known gene

29
Q

recall that secondary immunodeficiencies are not genetic but caused by external factors, what are the 4 main causes of secondary immunodeficiency?

A
  • malnutrition
  • medication
  • aging
  • disease
30
Q

explain malnutrition as a cause of secondary immunodeficiency

is this the most common cause?

A
  • most common cause

- deficeincy in one or more nutrients can result in improper functioning of the immune system

31
Q

what is the largest global cause of malnutrition?

A

protein calorie deficiency - where T-cell population decreases in proportion to protein levels, resulting in reduced ability to fight infection

32
Q

explain medication as a cause of secondary immunodeficiency

A

-cytotoxic agents (chemo/radiation therapy) target rapidly dividing cells in the body - this can supress immune system

  • immunosupressants are used to intenionally supress the IS (organ transplant/AI disease)
  • can completely supress IS
  • can increase susceptibility to opportunistic infections
33
Q

explain aging as a cause of secondary immunodeficiency

A
  • recall: thymus shrinks as you age so you’re producing fewer T-cells
  • why nutrition is more important in older people - especially calcium and zinc bc their deficiencies are common in the elderly (may be due to reduced ability of intestine to absorb them)
34
Q

explain disease as a cause of secondary immunodeficiency

A
  • prolonged/chronic disorders can cause secondary immunodeficiency due to stress placed on the immune system
  • e.g. diabetes - lymphocytes don’t function optimally in high blood sugar levels
  • e.g. bone marrow cancer decreases T/B-cell production
35
Q

what is HIV? why do we care?

A
  • ss retrovirus that’s transmitted through bodily fluids

- most studied case of secondary immunodeficiency

36
Q

recall: what is the process of an HIV infection?

A
  • requires fusion of the viral gp120 (envelope protein) to the CD4 receptor on T-cells, which permits HIV entry into the CD4+ T-cell
  • then HIV releases reverse transcriptase to convert its RNA into DNA
  • then it uses integrase to integrate HIV-DNA into T-cells genetic content in the nucelus
  • once integrated, HIV uses host machinery to make HIV proteins for assembly into immature HIV that buds out of the host cell
  • following release, HIV results in progressive destruction of helper T-cells
37
Q

what are the host cell surface receptors used by HIV?

A
  • CD4 = primary receptor for virus
  • CCR5 = coreceptor
  • CxCR4 = coreceptor
38
Q

what type of cells does HIV infect?

A

T-cells

39
Q

how does HIV viral DNA enter the host DNA?

A

interactions btwn virus and coreceptor allow virus uncoating, and entry of the viral nucleocapsid containing the viral genome into the cell

40
Q

what is the latency of an HIV infection?

A
  • after the virus enters the cell, RT copies RNA into ds DNA
  • integrase then mediates the integration of viral DNA into host cell chromosomal DNA
  • HIV is latent while integrated in host DNA (can persist in the cell in an inactive state)
  • reactivation of the virus occurs when the host cell is activated and viral transcription is initiated
41
Q

explain the creation of a new HIV particle

A
  • after viral transcription, viral mRNA forms thats translated into viral proteins
  • genome length transcripts of the virus also accumulate
  • these assemble into immature, non-infectious HIV particles at the host cell membrane
  • this then buds off
  • maturation of this new particle continues after it buds off from the host cell to create a new infectious particle with the same nucleocapsid morphology
  • specifically, HIV proteases within the viral particle cleave viral polypeptides which results in mature, infectious viral proteins
42
Q

what is the effect of HIV on infected cells?

A
  • budding process destroys the membrane of infected cells (cell death)
  • apoptosis is also induced in unaffected T-cells by overexpression of antigenic ligands (incl. gp120)
  • i.e., severly reduced number of CD4+ T-cells even though there’s a low number of infected T-cells
43
Q

the loss of CD4+ helper T-cells if central to the development of?

A

AIDS

44
Q

the loss of CD4+ helper T-cells contributes to abnormal production of?
what does this lead to?

A
  • IL-1 and TNF-a
  • leads to decreased proliferation in response to antigens
  • leads to decreased delaying hypersensitivity and cell-mediated immunity to viral, fungal and parasitic infections
  • addional infections further inhibit the immune response
45
Q

what are other immunological abnormalities associated with HIV? (5)

(other than low CD4+)

A
  • abnormal macrophage function (related to IL-1)
  • decreased NK cell activity
  • decreased CD8+ cytotoxic T-cells later in infection
  • increased non-specific Igs
  • increased auto-antibodies
46
Q

summarize the progression of an HIV infection

A
  • begins with mil flu-like symptoms
  • some may be asymptomatic (however theyre still infectious)
  • generalized lyphadenopathy is associated with early stages (enlargment of 2+ non-contagious lymph node groups)
  • slowly, immune function gets worse and the following may present:
  • pneumocytis carinii
  • kaposi’s sarcoma
  • non-hodgkin lymphoma
  • candidiasis
  • cytomegalovirus
  • dementia
  • death
47
Q

what are idiopathic immunodeficiency diseases?

A

those that have no known cause

48
Q

idiopathic immunodeficiency diseases are often?

A

B-cell immunodeficiencies

49
Q

what are the 2 most common idiopathic immunodeficiency diseases?

A

(1) common variable hypogammaglobulinemia
- affects 1 in 70,000 btwn age 15-35
- mostly defects in the antibody variable region
(2) selective IgA deficiency:
- affects 1 in 700
- can’t be treated with gamma globulins bc foreign IgA elicits an immune response

micr 386 (31 decks)

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