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Blood and Lymph > Week 5 > Flashcards

Week 5 Flashcards

1
Q

Capsule of lymph node

A

thin, fibrous (thickened/fibrotic in reactive or neoplastic conditions)

EX) Nodular sclerosis Hodgkin Lymphoma

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2
Q

Cortex of lymph node

A

contains lymphoid follicles (primary and secondary) and paracortex (interfollicular T cell zone)

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3
Q

Secondary follicle

A

mostly B cells

a. Mantle zone = small cells surrounding germinal center
- All B cells, small, uniform, tightly packed

  • CD20 (also CD 19 and 22) = B cell marker (highlights mantle zone B cells and germinal center B cells)

b. Germinal center: inner side
- Dark zone = mostly B cells (centroblasts)
- Light zone = mixed B cells (centrocytes), T cells, macrophages, and other cells
- BCL6 and CD10: markers specifically expressed in normal germinal B cells and derived lymphomas

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4
Q

Paracortex

A

mixed cell populations, mostly T cells

CD3 (also CD4, 5, 8)= T cell marker - shows them abundant in paracortex and scattered in germinal center

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5
Q

Sinuses

A

subcapsular, cortical, and medullary

1.Contain lymphocytes, plasma cells, and histiocytes

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6
Q

Lymphoma: Immature B cells:8c

A

B cell Acute Lymphoblastic Leukemia or Lymphoblastic Lymphoma (B-ALL/LBL)

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7
Q

Lymphoma: Mantle cell

A

Mantle Cell lymphoma

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8
Q

Lymphoma: Germinal Center B-Cell (3)

A
  1. Follicular Lymphoma
  2. Hodgkin Lymphoma
  3. Burkitt Lymphoma
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9
Q

Lymphoma: Pre or Post-Germinal Center B cell

A

Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL)

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10
Q

Lymphoma: Plasma cell myeloma

A

Plasma cell myeloma (multiple myeloma)

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11
Q

Lymphadenopathy and associated diseases (3)

A

lymph nodes of abnormal size, number or consistency

Associated diseases:

  1. CLL/SLL
  2. Follicular lymphoma - asymptomatic except for lymphadenopathy → late stage diagnosis usually
  3. Mantle Cell Lymphoma (MCL)
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12
Q

WHO classification of lymphomas (5)

A

Morphology, immunophenotype, genetic findings, location, and age

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13
Q

Clinical features of CLL and SLL

A
  1. CLL = most common leukemia (30% of all leukemias)
    a. Predominantly peripheral blood lymphocytosis
  2. SLL = 7% of Non-Hodgkin Lymphoma
    a. Predominantly extramedullary involvement (nodes)
  3. Median 65 years, male predominance (2:1 over females)
  4. Present asymptomatic, or mildly symptomatic
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14
Q

Morphology of CLL and SLL

A
  1. Mature Lymphocytosis > 5 x10^9/L sustained for at least 3 months
  2. Monocloncal B cell with immature phenotype
  3. CLL cells: small, round nuclei, clumped chromatin
  4. Lymph node involvement: effacement of nodal architecture with diffuse infiltration
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15
Q

Immunophenotype CLL and SLL

A
  1. Positive: CD5 and CD23 (t cell marker expressed by B cells - unique to this lymphoma),, CD19 (B cell)
  2. Weak: CD20, surface immunoglobulin, CD22, CD11c
  3. Negative: CD10, FMC7
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16
Q

Genetic alteration CLL and SLL (4)

A
  1. Deletion of 13q14
  2. Trisomy chr12
  3. Deletion 11q22-23
  4. Deletion 17p13
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17
Q

On a scale from 1-10, how much of a bitch is Charlie?

A

15***

*** Question adapted from USMLE Step I 2015 edition

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18
Q

Clinical features of follicular lymphoma (4)

  • origin
  • age
  • Location
  • stage of presentation
A
  1. Lymphoma of germinal center B cell origin
  2. Mostly Adults (median 60 years), male = female
  3. Location: lymph nodes mostly - also spleen, bone marrow, GI, skin
  4. Usually present with widespread stage III or IV disease at diagnosis
    a. Asymptomatic except for lymphadenopathy
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19
Q

Morphology of follicular lymphoma

A

1.Neoplastic follicles, uniform in size, evenly distributed in lymph node cortex and medulla

No tingible body macrophages, no dark zone or light zone

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20
Q

Immunophenotype of follicular lymphoma:
Positive for?
Negative for?

A

Positive For:

a. B-cell markers: CD19+, CD20+
b. BCL2+ positive (normally NO BCL2 in germinal center B cells)
c. Germinal center B-cell marker: CD10 and BCL6

2.Negative: CD5, CD23

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21
Q

Genetic alteration for follicular lymphoma

A
  1. t(14:18) in 75-90% of cases

a. BCL2 gene (chr18) placed under influence of IGH promoter on chr14 → persistent expression in B cells → Lymphoma

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22
Q

Clinical features of mantle cell lymphoma (6):

  1. % of NHL
  2. median age
  3. M:F ratio
  4. Location
  5. Stage
  6. Aggressiveness
A
  1. 3-10% of NHL
  2. Median age = 60 years
  3. M:F = 2:1
  4. Location: mostly lymph nodes - also spleen, bone marrow, GI
  5. Presents as stage III or IV with lymphadenopathy, hepatosplenomegaly

a. Can have bone marrow involvement
6. Moderately aggressive (in contrast to other small B-cell lymphomas)

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23
Q

Morphology of mantle cell lymphoma (3)

A
  1. Effacement of lymph node architecture
  2. Diffuse infiltration of lymphoma cells in node
  3. Tumor cells: small-medium size, irregular nuclei, small nucleoli
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24
Q

Immunophenotype mantle cell lymphoma:
Positive for?
Negative for?

A

Positive for:
a.B-cell markers: CD19, CD20

b. CD5, which is also positive in CLL/SLL (typically not expressed by B cells, but MCL B cells do express CD5)
c. Cyclin D1 (BCL1), which is negative in most of other B-cell lymphomas

Negative for:

a. CD23, which is positive in CLL/SLL
b. Germinal center B-cell markers: CD10, BCL6

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25
Q

Genetic alteration mantle cell lymphoma

A

t(11:14) involving BCL1 gene on 11q13 and IGH gene on 14q32

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26
Q

I’m sorry Charlie, I didn’t mean to hurt your feelings

A

I know you are sensitive

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27
Q

Clinical features of Burkitt lymphoma (BL) (3)

A
  1. Highly aggressive
  2. Presents at extranodal sites or as leukemic form
  3. Mostly in children or young adults
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28
Q

Endemic BL

  • geographic location
  • age
  • involvement
  • % EBV positive
A

a. Malaria belt in Africa
b. Childhood malignancy (4-7 years of age)
c. Involves jaw or abdomen
d. 95% EBV positive

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29
Q

Sporadic BL

  • age
  • involvement
  • % EBV infection
A

a. Mostly in children and young adults
b. Mostly in ileocecal area
c. 30% EBV infection

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30
Q

Immunodeficiency BL

A

HIV patients

a.30% EBV infection

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31
Q

Morphology of Burkitt lymphoma cells

A

Medium sized, round nuclei, one or several small nucleoli, deeply basophilic cytoplasm with vacuoles

-Diffuse infiltration of monomorphic, medium sized cells with “starry sky” pattern

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32
Q

Immunophenotype Burkitt lymphoma:

Positive for:
Negative for:

A

Positive for:

a. B cell Markers: CD19, CD20
b. Germinal Center B-cell markers: CD10, BCL6
c. High proliferation index
d. EBV positive in endemic BL (sometimes + in sporadic/immune)
e. MYC gene

Negative for: CD5, CD23, BCL2, TdT

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33
Q

Genetic alteration Burkitt Lymphoma

A

t(8;14) - juxtaposes MYC gene at 8q24 next to IGH promoter

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34
Q

Clinical features of diffuse large B-cell lymphoma:

  1. size
  2. % NHL cases
  3. age
  4. m:f
  5. where does it grow
  6. aggressiveness
  7. treat
  8. different types?
A
  1. Diffuse proliferation of medium to large-sized neoplastic B cells
  2. Most common type of non-Hodgkin’s Lymphoma (31% of cases)
  3. Median age = 64 years
  4. Slight male predominance
  5. Rapidly growing nodal (70% of the time) and extranodal (30% of the time) tumor
  6. More aggressive than other low-grade B-cell lymphomas
  7. Potentially curable with standard chemo (46% survival)
  8. Many different types of large B-cell lymphoma
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35
Q

Morphology of diffuse large b cell lymphoma

A
  1. Complete effacement of architecture of lymph nodes by diffuse lymphoma cell infiltrates
  2. Large-sized lymphoma cells, with nuclear size greater than histiocyte nucleus or small lymphocyte
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36
Q

Immunophenotype diffuse large B cell lymphoma

A

B-cell markers positive: CD19+, CD20+

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37
Q

Indolent (causing little to no pain) lymphomas

A

Small B-cell lymphomas mostly indolent (except MCL)

  1. CLL/SLL
  2. Follicular Lymphoma
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38
Q

Aggressive lymphomas

A

i. MCL = moderately aggressive

ii. Diffuse Large B-Cell Lymphoma (slightly more aggressive than other low-grade B-cell lymphomas)

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39
Q

Highly aggressive lymphomas

A

Burkitt’s Lymphoma - highly aggressive but potentially curable (60% cure)

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40
Q

4 common types of lymphomas in adults

A

i. CLL/SLL
ii. Follicular Lymphoma (FL)
iii. Mantle Cell Lymphoma (MCL)
iv. Diffuse Large B-Cell Lymphoma

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41
Q

Common types of lymphomas in children

A

Burkitt’s Lymphoma (endemic and sporadic)

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42
Q

BCL2 gene arrangement

A

Overexpression of BCL2 → massive follicular lymphoid hyperplasia, but not enough to cause neoplastic transformation

Normally no BCL2 in germinal center B cells

Follicular Lymphoma: BCL2 gene (chr18) placed under influence of IGH promoter on chr14 → persistent expression in B cells

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43
Q

BCL1 gene arrangement

A

involved in cell-cycle progression

  1. Cyclin D1 binds CDK4 and CDK6 → phosphorylation of Rb → release E2F1-3 transcription factors → activate genes that are required for cell cycle progression → G1/S transition → cell divides
  2. Mantle Cell Lymphoma:
    a. Strongly/diffusely positive Cyclin D1 (BCL1) (which is negative in most of other B-cell lymphomas)
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44
Q

MYC gene arrangement

A

TF, overexpression can induce carcinogenesis of lymphoma development

Burkitt’s Lymphoma

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45
Q

Type IV immunopathology

examples?

A

T cell mediated immunity and delayed hypersensitivity

DO NOT require B cells - antibody is NOT involved in primary process

EX) rejection of allografts, graft vs. host disease (the reverse of allograft rejection), (+) TB skin test, resistance to Mycobacterium tuberculosis, resistance to fungal infections, contact dermatitis, etc.

46
Q

TB skin testing

If patient is TB+…

A

1) Mantoux skin test, 0.1 ml of PPD (purified protein derivative) preparation of M. tuberculosis antigens (tuberculin)
2) Injected intradermally →
3) antigen taken up by local APCs, onto MHC class II
4) IF patient has anti-TB Th1 memory cells → secrete IFN-y, attract macrophages → firm, raised induration

47
Q

_________ are the predominant cells present in biopsied site at 48 hrs if TB infection is present

A

Macrophages

48
Q

Why are tiny doses of TB skin tests NOT immunizing?

A

antigen needed to elicit a positive reaction in an immune person is MUCH LESS than needed to immunize

49
Q

Why would a person have a false positive PPD test?

A

If they had the TB immunization (given in foreign countries, but not US)

50
Q

Poison Ivy exposure: immunization phase

A

Initiation of immune response following first exposure

1) Contact dermatitis with oil Toxicodendron radicans → compound penetrates skin and becomes associated with MHC on APCs
2) APC → lymph node → present MHC+antigen to THo → develop into/proliferate Th1 and Th17 cells → create memory T cells
3) By the time you became immunized, antigen may be gone already, and you may have never noticed

51
Q

Poison Ive Effector Phase

A

Elicitation of a reaction in a person who is ALREADY immunized

1) Months later, encounter poison ivy again
2) Oil on skin → MHC on APCs → memory T cells rapidly expand and get activated in area of contact
3) Memory T cells have a lower activation threshold - less antigen for elicitation of reaction
4) → secrete IFN-y → attract macrophages → firm red area of inflammation in 6-12 hours, peak at 24-48 hours = DELAYED-type hypersensitivity

52
Q

Why would a small chemical or peptide not need to be processed through an APC to be presented by an APC to T cells?

A

Typically: Processing of antigen required to reduce antigen to an epitope-sized particle capable of interacting with the MHC.

1) BUT if antigen is already reduced to the size of the epitope, as with small chemicals or peptides, it may associate directly with the MHC without processing.
2) Antigens can also bind to a peptide which is then presented on an MHC

53
Q

HLA-B*5701 and HIV drug abacavir

A

Abacavir = nucleoside reverse transcriptase inhibitor

HLA-B*5701 = class I MHC

Abacavir hypersensitivity syndrome → drug induced autoimmune reaction

T cell immune response

Now we test for HLA-B*5701 allele before offering drug

54
Q

How do we measure T cell immunity in vitro?

A

Whole blood or isolated WBCs (T cells + APCs) incubated with antigen in cell culture → observe cell proliferation, cell size, DNA synthesis, cytokines

EX) QuantiFERON-TB Gold test

55
Q

QuantiFERON-TB Gold test

A

1) Purified TB human-specific antigen (NOT cow like in PPD) proteins added to sample of whole blood (in vitro)
2) Incubated → IFN-y levels measured with ELISA

Test negative in people vaccinated with BCG (cow TB)→ can distinguish between infection and previous immunization.

Test positive if sufficient T cells against human M. tuberculosis

56
Q

First set graft reaction

A

Graft rejection in 10-20 days

5-10% of recipient’s T cells recognize the graft MHCs as self MHC+antigen → become activated → produce more anti-graft Th1 and CTL → rejection

Typical pathway of rejection

57
Q

Second set graft rejection

A

Faster rejection with second exposure - due to T cell memory developed during first exposure

Rejected in 5-10 days

58
Q

Hyperacute Rejection

A
  • Graft rejected before it even has time to “heal in.”
  • “White graft” reaction because graft stays white and bloodless.
  • Results from development of abs against histocompatibility antigens
  • Common with xenografts
59
Q

The brain is _______, but not ___________

A

antigenic, but not immunogenic

60
Q

Why is the brain antigenic, but not immunogenic?

A

No brain protein presented in thymus for negative selection of anti-brain T cells
→ anti-brain T-cells exist in everyone’s T-cell repertoire, BUT are rarely stimulated, b/c brain well defended and well protected.

IF T-cells somehow stimulated against the brain –> becomes immunogenic → T cells will attack it

61
Q

What are some examples of the brain becoming immunogenic?

2

A
  • Meat packing plant: inhaled pig brain particles –> pig brain presented to T cells –> cross reacted with human brain –> T cells start attacking human brain
  • MS: researcher got brain in a cut –> gradual encephalopathy
62
Q

Sjogren Syndrome: autoimmune reaction against ________ involving _______

A

exocrine glands (tears, saliva)

CTL

63
Q

Type 1 Diabetes involves _______ cells and _______ and is associated with HLA-____ and _____

A

T cells

ab creating to B-cells in pancreatic insnulin-producing islets

HLA-DQ2 and DQ8

64
Q

Rheumatoid Arthritis

A

most common autoimmune disease

exact pathogenesis not known, but we know that Rheumatoid factor makes human IgG agglutinate

Rituximab is an effective treatment (CD20 inhibitor)

65
Q

Three conditions must be met for graft versus host disease to occur

A

1) Graft must contain immunocompetent T-cells (even BM has mature T cells)
2) There must be at least one antigen in host which graft’s T-cells can recognize
3) Host must be relatively immunoincompetent or unable for genetic reasons to recognize the graft’s MHC antigens.

66
Q

Acute GvHD

presentation?
treatment?

A

develops in 2-10 weeks after BM transplant

Maculopapular skin rash, diarrhea, hepatic inflammation with jaundice, infections

Treat with anti-inflammatory drugs (corticosteroids, immunosuppressives)

67
Q

Chronic GvHD

A

develops in months to years

Can occur even in patient with perfect HLA match
–> Against minor histocompatibility antigens

Chronically activated T cells pouring out cytokines → compromised regulation → autoimmunity can result

68
Q

Graft-Versus-Leukemia Phenomenon

A

Leukemia patient stops responding to conventional therapy → LARGE doses of drugs or radiation (myeloablative - destroys all bone marrow) → take marrow from best matched allogeneic donor

Least GvHD with BM from themselves stored pre-treatment or T-depleted allogeneic marrow, BUT higher rate of leukemia relapse

Graft vs. Leukemia reaction thought to be important part of the success of the bone marrow transplant

Maximize GvL, minimize GvH

69
Q

Th2 Cells in Immunopathology

A

Th2 cells found in periphery of certain inflammatory and infectious states, especially asthma and chronic worm infestations

Activate M2 macrophages and eosinophils → fibrosis (chronic), more intense inflammation

70
Q

Plasma Cell Neoplasms:

Clonal proliferation of _________ that secrete _________. can present with ________ or _______ tumors

A

Ig-producing plasma cells from bone marrow

a SINGLE class of Ig

Bone marrow or extramedullary tumors

71
Q

Morphological features in plasma cell myeloma (2)

A

Rouleaux formation when M protein markedly elevated

Plasma cells found on blood smears

72
Q

Clinical features of plasma cell myeloma (multiple myeloma)

A

1) Secondary involvement of other organs possible
2) Can be asymptomatic to highly aggressive
3) Presents as bone pain in back or extremities
4) 90% of patients over 50 years of age

73
Q

Radiographic findings of plasma cell myeloma (2)

A

Lytic lesions

Osteoporosis or fractures (vertebra, pelvis, skull, rib, femur, proximal humerus)

74
Q

Lab findings of plasma cell myeloma (3)

A

M protein in serum or urine - protein electrophoresis

Associated symptoms (CRAB - hypercalcemia, renal insufficiency, anemia, bone lesions)

Monoclonal plasma cells in marrow (> 10%)

75
Q

Solitary Plasmacytoma of bone

A

Localized tumor of bone composed of clonal plasma cells similar to those of plasma cell myeloma

NO bone marrow involvement

SINGLE bone lesion of monoclonal plasma cells

NO other bone lesions, NO M protein, normal Ig levels, NO myeloma related symptoms

76
Q

Extraosseous Plasmacytoma

A

Localized plasma cell tumors that arise outside the bone marrow

Common in upper respiratory tract (nasal passages, sinuses, oropharynx, larynx)

Mean age of diagnosis is 55 years, ⅔ male

77
Q

MGUS = Monoclonal Gammopathy of Undetermined Significance

Presence of ______ with NO evidence of…

A

monoclonal Ig (M protein) in serum or urine

NO evidence of plasma cell myeloma [NO lytic bone lesions,

78
Q

Both solitary plasmacytoma and extraosseous plasma cytoma have normal __________

A

normal serum M protein
no other bone lesions
No myeloma related symptoms

79
Q

MGUS is a precursor of ___________

A

plasma cell myeloma

80
Q

Smoldering/Indolent myeloma

A

Associated symptoms (CRAB - hypercalcemia, renal insufficiency, anemia, bone lesions)

81
Q

Classical Hodgkin Lymphoma (CHL) is a proliferation of __________ which stain + for _____ and _____ but NOT ______

A

germinal center B-cells

CD30+, CD15+, CD45-

82
Q

Classical Hodgkin Lymphoma (CHL) includes 4 subtypes

A

Nodular Sclerosis
Lymphocyte Rich
Mixed Cellularity
Lymphocyte Depleted

83
Q

Nodular Sclerosis CHL:

Occurs at what age/sex?
Where in the body?

A

Most frequent subtype of CHL
Mostly in young adults (females)
Typically occurs above the diaphragm

84
Q

Morphology of Nodular sclerosis (3)

A

Thickened lymph node capsule

Nodular areas surrounded by broad bands of collagen

Lacunar cells

85
Q

Lymphocyte-Rich CHL (4)

A

5% of CHLs

Nodular growth pattern with residual germ centers

Few RS cells

Best prognosis

86
Q

Mixed Cellularity CHL (5)

A
  • Any age
  • Second most common CHL
  • Below or on both sides of the diaphragm
  • Lack broad bands of collagen seen in nodular sclerosis CHL
  • EBV+ 75%
87
Q

Lymphocyte Depleted CHL (4)

A
  • Less than 1% of CHLs
  • Numerous RS cells - anaplastic and bizarre appearing
  • Usually EBV+
  • Worst prognosis
88
Q

Reed-Sternberg Cells are typically present in ________

A

CHL

89
Q

Reed-Sternberg Cells stain + for ______ and _____, but - for __________

A

CD30+, CD15+, CD45-

90
Q

Reed-Sternberg Cell morphology

A

Large (10x size of lymphocytes), contains multiple nuclei or large lobulated nucleus

Nuclei show accentuated membrane, pale chromatin, single large eosinophilic viral-inclusion-like nucleus

Ample and amphophilic cytoplasm

91
Q

TGF-B + IL-6 is secreted when ________ and cause Tho cells in Peyer’s Patches to differentiate into…

A

aggressive invaders cause epithelial cells to secrete IL-6

Th1, Th2, Th17 and suppress Treg

92
Q

TGF-B + IL-10 is secreted in __________ and cause Tho cells in Peyer’s Patches to differentiate into…

A

the normal gut

Treg

93
Q

Why do we want a lot of Tregs in our gut Peyer’s Patches normally?

A

Want lots of Treg in gut- constant exposure to bacteria and food derived non-pathogenic potential immunogens coming through M cells of gut

94
Q

Chronic Frustrated Immune Response

A

immune system can’t get rid of foreign antigen → remains chronically active

NOT autoimmune

95
Q

Crohns disease

A

small intestine (terminal ileum), fistulas common, patchy areas infection interspersed with healthy ones

96
Q

Ulcerative Collitis

A

large intestine, can erode surface leading to bleeding

97
Q

In both CD and UC there is a…

A

dysregulated T cell immune responses to commensal bacteria

Th1, Th17, and Th2 activated against normal commensal organisms

98
Q

What influences IBD occurence

A

Environment
Genetics (163 loci associated with increased risk)
bad luck

99
Q

Gluten

A

found in certain grains (wheat, rye barley) = antigen T cell responds to

Very branched, contain lots of prolines

Can return gut to normal by avoiding gluten

100
Q

Antibody involvement in Celiac Disease

A

IgA ab made to tTg2 when it is covalently linked to gluten “antigen”

Abs not pathogenic in gut - T cell response causes symptoms in gut

Abs to tTG3 (cross reactive with tTG2) can cause skin symptoms (Dermatomyositis)

101
Q

T cell involvement in Celiac Disease

A

tTG2 + gluten peptide (gliadin) taken up into B cells and presented to T cells → autoimmune response to tTG2

T cell immunity to gluten (gliadin) peptides → chronic inflam

102
Q

HLA alleles ______ and _____ are associated with celiac disease because…

A

HLA-DQ2 and HLA-DQ8

DQ8 and DQ2 are weirdly shaped so are good at presenting gliadin which is also weirdly shaped (prolines) to T cells

BUT not all HLA-DQ2 or 8 people get Celiac

103
Q

Autoimmune aspect of Celiac Disease

A

Must break down gluten with tTG2

Short lived intermediate covalently linking tTG2 and gluten → autoantibodies made to tTG2 and tTG2 presented to T cells

104
Q

Non-autoimmune aspects celiac

A

NOT an autoimmune disease because it is a foreign antigen (gluten)

T-cells respond to gluten (antigen) causing chronic inflammation

105
Q

tTG2

A

enzyme

Makes protein cross-links through glutamines

In some people it couples to, but can’t release, digestion-resistant glutamine-rich gliadin (wheat) peptides → becomes B-cell autoantigen

Foreign + self hybrid antigen mechanism

106
Q

Chronic Beryllium Disease

A

Pulmonary inflammatory and fibrotic disease caused by exposure to inhaled Beryllium dust (miners, machinists, nuclear industry)

Be becomes covalently linked to normal peptides in blood → creates novel epitopes to which Th1 response is made → Th2 response later (scarring)

Be cannot be removed by macrophages → chronic, even though it was a single exposure

No way to get Be out of the body

107
Q

Psoriasis

A

Chronic Frustrated Immune Response

involves TH17 (IL-17 and IL-23 especially)

108
Q

Peridontal Disease

A

Chronic Frustrated Immune Response

bugs get into gingival crevice, T cells can’t get there so you get chronic inflammatory disease (T cells can’t get the upper hand)

109
Q

Hygiene Hypothesis

A

Trying to explain why there is an increase in allergy and asthma in rich countries and less increase in poor countries

Exposure to environmental dirt and infections helps immune system mature normally, BUT lack of exposure can leave a child in an infantile state

Not enough evidence to support it

110
Q

Old Friends Hypothesis

A

Certain harmless microorganisms have been in humans for so long we rely on their presence to instruct our immune systems not to overreact against commensals or low-grade pathogens

Adequate exposure to these “old friends” → develop balance between activation and regulation

Inadequate old friend exposure, “old friendless” → too few Tregs, and too many Th1, Th2, Th17 response to some benign organism

111
Q

Switch Th1/Th2/Th17 to Treg instead?

A

Treat with Whipworms
Increase in Treg in the gut can suppress Th1, Th17, and Th2 responses

Treg suppression is NOT antigen specific, many nearby T cells down-regulated or do not differentiate into effectors

Blood and Lymph (9 decks)

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