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BL and DD Unit 3 > Immunology > Flashcards

Immunology Flashcards

1
Q

What is the difference between primary and secondary immunodeficiency?

A

Primary - mutations in genes required for normal development of immune system (e.g. congenital defect in thymus or bone marrow); basically congenitally

Secondary - follows treatment with IS drugs or in an IS disease like AIDS; basically acquired

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2
Q

What is SCID?

A

Severe Combined Immunodeficiency Disease

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3
Q

What are the signs of SCID?

A
  • lymphopenia of T and B cells
  • absent thymic shadow on xray
  • small tonsils
  • mitogen responses low
  • serum Ig low
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4
Q

What happens in SCID-X1?

A

SCID-X1

  • defect in the gene for gamma chain that forms part of IL-2 receptors and other cytokines needed for lymphoid development
  • block from SCH to SCL
  • lymphocytes don’t mature
  • X-linked recessive
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5
Q

What happens in

Adenosine Deaminase Deficiency?

A
  • autosomal recessive type of SCID
  • lack adenosine deaminase –> adenosine accumulates in cells and impairs lymphocyte development
  • can give blood transfusion, but must irradiate first to kill any T cells
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6
Q

What is Bruton’s disease?

A
  • X-linked Agammaglobulinemia
  • normal T cells, but low B cells
  • due to a developmental block between pre-B cell and B cell formation
  • protein tyrosine kinase in pre-B cells is defective
  • see lots of bacterial infections –> pneumonia and diarrhea
  • enteroviruses can go through mucous membranes since no IgA to protect
  • viral infections not a problem since have T cells
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7
Q

What happens in X-linked hyperIgM syndrome?

A
  • have high IgM and low IgG and IgA
  • defect in IgM to IgG switching
  • Tfh has CD154 or CD40-ligand that interacts with CD40 on B cells to activate them and switch to IgG
  • if CD40 or CD40-ligand is defective, then don’t make IgG
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8
Q

What happens in Common Variable Immunodeficiency?

A
  • normal pre-B cells and B cells (and T cells), but lack maturation to plasma cell
  • low IgG
  • recurrent bacterial infections since low antibodies
  • treat with IVIG or SCIG
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9
Q

What happens in DiGeorge syndrome?

A
  • thymus develops from 3rd and 4th pharyngeal pouches; if defective, then T cells are absent
  • 45 gene deletion on chromosome 22
  • parathyroid also affected, so can see hypocalcemic seizures
  • abnormal development of heart as well
  • see viral and fungal infections
  • T cells low, meaning B cells fail to get activated as well
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10
Q

CATCH-22

A

Calcium: low due to parathyroid defect

Appearance: head and face deformities

Thymus: no thymus

Clefts palate

Heart: abnormalities

on chromosome 22

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11
Q

What kinds of infections are seen in T cell and B cell deficiencies?

A

T cell def: viral, yeasts, fungal (Candida albicans, P. jirovecii)

B cell def: high grade (extracellular, pus) bacteria like S aureus, H influenzae, S. pneumoniae

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12
Q

What happens in transient hypogammaglobulinemia of infancy?

A
  • 6mo-18mo after birth
  • slow to produce IgG after stop receiving from mom
  • have lots of bacterial infections
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13
Q

What is selective IgA deficiency?

A
  • most common ID disease (200/100000)
  • usually asymptomatic, but can have diarrhea and sinopulmonary infections and allergies
  • some familial tendency
  • more common in people with celiac disease
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14
Q

What is ataxia telangiectasia?

A
  • AR inheritance
  • sinus infetions, pneumonia, ataxia, and telangiectasia
  • T and B cell def
  • IgA def
  • also defect in DNA repair –> tumors
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15
Q

What is wiskott-aldrich syndrome?

A
  • platelet and b cell def
  • eczema
  • bacterial infections
  • X-linked
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16
Q

How do you treat immunodeficiency?

A

1) Isolation - not practical for long time
2) Prophylactic antibiotics - change regularly to avoid resistance
3) IVIg (when B cell def) - mostly IgG
4) Transplant - thymus in DiGeorge; bone marrow or purified stem cells for SCID; ADA with PEG for ADA def

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17
Q

Briefly describe Type I immunopathology

A
  • due to IgE

- Th2 mediated events

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18
Q

Briefly describe Type II immunopathology

A
  • due to IgG, IgM, and IgA causing harm to self (autoantibodies)
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19
Q

Briefly describe Type III immunopathology

A
  • formation of immune complexes trapped in basement membrane of blood vessels that activate complement –> vasculitis
  • in chronic type III, T cells are important
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20
Q

Briefly describe Type IV immunopathology

A
  • pathologies due to T cell responses, both helper and cytotoxic
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21
Q

Briefly describe CFIR immunopathology

A
  • chronic frustrated immune response
  • body is using adaptive immunity to get rid of antigens that it never can
  • e.g. gut flora (Crohn disease), skin flora (psoriasis), chemicals (Be disease), foods (celiac disease)
  • can’t dispose or effectively wall of antigen
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22
Q

What are the 3 ways that antibodies can damage self tissue?

A

1) Neutralization
2) Complement-mediated damage
3) Stimulatory hypersensitivity

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23
Q

What is neutralization?

A
  • human protein inactivated by an antibody

- IFNgamma antibodies exist for example

24
Q

How does complement-mediated antibody tissue damage work?

A
  • antibodies made against tissue

- activate complement and cells damaged by lysis, phagocytosis, or release of lysosomal enzymes and ROS from phagocytes

25
Q

What is stimulatory hypersensitivity?

A
  • if auto antibody against a cell surface receptor, can act as an agonist and activate it
26
Q

What happens in Graves disease?

A
  • IgG antibody to thyroid stimulating hormone receptor –> mimics TSH and secretes thyroid hormones and bypasses normal neg feedback from pituitary –> hyperthyroidism/Graves disease
  • example of stimulatory hypersensitivity
27
Q

What happens in myasthenia gravis?

A
  • progressive muscle weakness
  • antibody to acetylcholine receptor –> activates complement and and attracts neutrophils and have inflammation
  • AIRE usually expresses CHRNA1, but there is an allele to CHRNA1 that doesn’t interact with AIRE –> Th clones that react with achr are not deleted by neg selection –> Tfh can help B cells make antibody to achr
  • hyperplastic thymus
  • treat with thymectomy, immunosuppression, IVIg
  • destruction of ACHRs
28
Q

What happens in goodpasture syndrome?

A
  • auto Abs to lung and kidney basement membrane
  • epitope on type IV collagen in BM of lung and kidneys
  • persistent glomerulonephritis, pulmonary hemorrhages
  • sharp and linear immunofluorescence because Abs line up literally on basement membrane
29
Q

What is dressler syndrome?

A
  • after an MI, people make an auto Ab against pericardial or myocardial antigens
  • presents with cardiac pain, fever, malaise, pericardial effuson
  • treat with anti-inflammatory agents
30
Q

What happens in rheumatic heart disease/rheumatic fever?

A
  • after a strep infection, cross reaction between Group A Strep M protein antigen and a structure on heart endothelial lining, probably laminin in valves (Abs made to fight bug, but also binds to antigens in heart)
  • followed by complement and neutrophil-mediated tissue destruction
  • rheumatic fever is more widespread affecting skin and CNS
31
Q

What happens in autoimmune thrombocytopenic purpura (ATP)?

A
  • bleeding due to destruction of platelets by auto Abs
  • treat with IS or removal of spleen
  • seen usually weeks after a viral infection in young people
32
Q

What happens in autoimmune hemolytic anemia (AIHA)?

A
  • usually follows a viral infection
  • penicillin and other drugs can cause AIHA
  • auto Abs against RBCs
33
Q

What happens in Hashimoto disease?

A
  • leading cause of hypothyroidism
  • antigen is thyroglobulin (where iodine is stored) and thyroid peroxidase
  • inflammatory and destructive due to antibodies and T cells)
34
Q

What is tolerance?

A

When the body does not create an immune response to an antigen (important especially to self antigens)

35
Q

What happens with hybrid antigen formation?

A
  • say you have a B cell that attacks self
  • normally you would be fine if T dependent and did not have Tfh cells to help
  • but if B cells binds to epitope that has self and foreign parts (specifically binding to the self part)
  • it then ingest the antigen
  • the FOREIGN epitope is presented on the surface to a Th2 cell on MHC Class II
  • Tfh releasese cytokines and activates B cell, which secretes more antibodies to self
36
Q

What is the forbidden clone?

A
  • when T cells against self bypass selection in the thymus and encounter self antigen
  • seen in myasthenia gravis
37
Q

How do you diagnose type II immunopathologies?

A
  • immunofluorescence
  • direct test: looking for Abs in the patient’s tissues; add anti-Ab that binds to antibodies on patients tissues if present and light up; need patients tissues
  • indirect: only with serum and normal tissue; (e.g. normal kidney tissue with no Ab, patients serum has anti kidney Abs, labeled anti-Ab bind to anti kidney Abs and light up)
38
Q

What is type IV hypersensitivity?

A
  • t-cell mediated
  • do not require Ab or B cells
  • delayed hypersensitivity
39
Q

Briefly describe the initiation and elicitation phases of a reaction

A

Initiation: response to first exposure of an antigen

Elicitation: reaction after already being immunized

40
Q

Describe what happens during initiation in contact dermatitis with poison ivy

A
  • urushiol goes through skin and MHC on dendritic cells presents to T cells in lymph nodes
  • produce Th1 and Th17 and divide but by the time they are in circulation, the urushiol is usually gone
41
Q

Describe what happens during elicitation during contact dermatitis with poison ivy

A
  • urushiol rubs onto skin again and goes onto APC
  • memory T cells from previous are throughout body and get activated in local area
  • secrete IFNgamma to bring in macrophages
  • not immediate, take a while
42
Q

Explain the tuberculin skin test

A
  • inject TB antigens intradermally
  • if there are memory cells for TB present (indicating a prior immunization or infection), then you see a large bump (15mm)
  • the bump is mainly macrophages
  • the injected dose is enough to evoke an elicitation reaction but not an immune reaction
43
Q

How does the QunatiFERON-TB Gold test work?

A
  • helps distinguish between previous immunization and infection
  • only human specific epitopes of TB proteins added to blood sample and IFNgamma measured
44
Q

How does abacavir hypersensitivity work?

A
  • if patient has HLA-B*5701, not recognized by Th1, then structure of that is changed by abacavir so that it binds self-peptides that are not usually presented –> drug induced AI
45
Q

Explain multiple sclerosis

A
  • brain is antigenic but not immunogenic because activated T cells will never get past blood brain barrier because APCs do not pick up antigen
  • fi you make brain antigens presented to APCS in a normal way, then can make activated T cells that can get through BBB
46
Q

What is CFIR?

A

Chronic frustrated immune response

- immune system is trying to get rid of a foreign antigen that it can’t eliminate or encapsulate

47
Q

How is IBD related to CFIR?

A
  • have abscesses in wall of intestine and inflammation

- patient activates Th1, Th17, and Th2 against gut bacteria but can’t get rid of them so continuous inflammation

48
Q

Describe the immune activity of the gut

A
  • lot of TGFbeta in peyer patches and IL-10 production by dendritic cells –> turns Th0 to Treg
  • lots of Treg cells
  • Tfh in PPs that drive B cells towards making IgA
  • however combining TGFbeta and IL-6 (produced by epithelial cells in response to damage) can downreg Treg and upreg Th1, Th2, and Th17
49
Q

What happens in celiac disease?

A
  • antibody to gut endomysium, specifically TG2
  • turns into a B cell autoantigen
  • T cell immunity to gliadin peptides that cause inflammation
50
Q

What happens in chronic Be disease?

A
  • pulmonary inflammation and fibrosis

- Be inhaled covalently links to peptides and creates new epitopes that Th1 responds to and Th2 scarring

51
Q

What happens in psoriasis?

A
  • unregulated T cell response to normal skin flora
52
Q

What happens in periodontal disease?

A
  • bacteria can get stuck in gingival crevice where saliva can’t really reach well and T cells definitely can’t because it is outside of the body
  • have shift from TBFbeta to adding IL-6 –> inflammation
53
Q

What is the hygiene hypothesis?

A
  • exposure to environmental dirt and infections helped the immune system mature normally, while lack of it leaves the child in an infantile state
  • thought that you would keep a Th2 dominated system like in babies, but saw also an increased risk in Th1 diseases
54
Q

What is the old friends hypothesis?

A
  • certain microorganisms have been in us so long that they tell our immune systems to not overreact against them
  • if you have adequate exposure to these guys, you have a balance between activation and regulation by Tregs
  • otherwise, might not have enough Tregs and make a too strong Th1 or Th2 response
55
Q

What do whipworms do?

A
  • apparently help increase Treg in gut and suppress Th1,17,2

BL and DD Unit 3 (11 decks)

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