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USMLE 1 > Immunology- Lymphoid structures and cellular components > Flashcards

Immunology- Lymphoid structures and cellular components Flashcards

1
Q

Immune system organs

1° organs:

A

Bone marrow—immune cell production, B cell maturation.

Thymus—T cell maturation

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2
Q

Immune system organs

2° organs:

A

ƒƒ Spleen, lymph nodes, tonsils, Peyer patches

ƒƒ Allow immune cells to interact with antigen

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3
Q

Lymph node

Follicle

A

Site of B-cell localization and proliferation. In outer cortex.

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4
Q

Lymph node

Medulla

A

Consists of medullary cords (closely packed lymphocytes and plasma cells) and medullary sinuses

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5
Q

Lymph node

Paracortex

A

Houses T cells. Region of cortex between follicles and medulla. Contains high endothelial venules through which T and B cells enter from blood.

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6
Q 
Lymphatic drainage associations
Cervical 
Mediastinal
Hilar 
Axillary
Celiac
Superior mesenteric
A
  1. Head and neck
  2. Trachea and esophagus
  3. Lungs
  4. Upper limb, breast, skin above umbilicus
  5. Liver, stomach, spleen, pancreas, upper duodenum
  6. Lower duodenum, jejunum, ileum, colon to splenic flexure
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7
Q 
Lymphatic drainage associations
Inferior mesenteric 
Para-aortic 
Internal iliac
Superficial inguinal
Popliteal
A
  1. Colon from splenic flexure to upper rectum
  2. Testes, ovaries, kidneys, uterus
  3. Lower rectum to anal canal (above pectinate line), bladder, vaginab(middle third), cervix, prostate
  4. Anal canal (below pectinate line), skin below umbilicus (except popliteal area), scrotum, vulva.
  5. Dorsolateral foot, posterior calf
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8
Q

Spleen- Components

A

ƒƒ T cells are found in the periarteriolarlymphatic sheath (PALS) within the white pulp.
ƒƒ B cells are found in follicles within the
white pulp.
ƒƒ The marginal zone, in between the red pulp and white pulp, contains macrophages and specialized B cells, and is where APCs capture blood-borne antigens for recognition by lymphocytes.

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9
Q

Splenic dysfunction

A

lower IgM
lower complement activation
susceptibility to encapsulated organisms.

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10
Q

Postsplenectomy blood findings:

A 
ƒƒHowell-Jolly bodies (nuclear remnants)
ƒƒ Target cells
ƒƒ Thrombocytosis (loss of sequestration and
removal)
ƒƒ Lymphocytosis (loss of sequestration
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11
Q

Thymus

A

Thymus is derived from the Third pharyngeal pouch.

Cortex is dense with immature T cells; medulla is pale with mature T cells and Hassall corpuscles.

Normal neonatal thymus “sail-shaped” on CXR.

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12
Q

Thymoma

A

neoplasm of thymus. Associated with myasthenia gravis and superior vena cava syndrome.

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13
Q

Hypoplastic thymus in…

A 
DiGeorge syndrome and severe
combined immunodeficiency (SCID).
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14
Q

Innate immunity

COMPONENTS

A

Neutrophils, macrophages, monocytes, dendritic cells, natural killer (NK) cells (lymphoid origin), complement, physical epithelial barriers, secreted enzymes.

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15
Q

Innate immunity
KEY FEATURES IN PATHOGEN
RECOGNITION

A

(TLRs): (PAMPs)

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16
Q

Innate immunity

SECRETED PROTEINS

A

Lysozyme, complement, C-reactive protein (CRP), defensins.

17
Q

Adaptative immunity

COMPONENTS

A

T cells, B cells, circulating antibodies

18
Q

MHC I

  • Loci
  • binding
  • expression
  • Function
A
  • HLA-A, HLA-B, HLA-C
  • TCR and CD8
  • All nucleated cells, APCs, platelets Not on RBCs
  • Present endogenously synthesized antigens (eg,
    viral or cytosolic proteins) to CD8+ cytotoxic T cells
19
Q

MHC II

  • Loci
  • binding
  • expression
  • Function
A
  • HLA-DP, HLA-DQ, HLA-DR
  • TCR and CD4
  • APCs
  • Present exogenously synthesized antigens (eg,
    bacterial proteins) to CD4+ helper T cells.
20
Q

HLA subtypes associated with diseases

A3

A

Hemochromatosis

21
Q

HLA subtypes associated with diseases

B27

A

PAIR:
Psoriatic arthritis, Ankylosing spondylitis,
IBD-associated arthritis, Reactive arthritis

22
Q

HLA subtypes associated with diseases

B8

A

Don’t Be late(8), Dr. Addison, or else you’ll send my patient to the grave.

Addison disease, myasthenia gravis, Graves disease

23
Q

HLA subtypes associated with diseases

DR2

A

Multiple hay pastures have dirt:

Multiple sclerosis, hay fever, SLE, Goodpasture syndrome

24
Q

HLA subtypes associated with diseases

DR3

A

Diabetes mellitus type 1, SLE, Graves disease,

Hashimoto thyroiditis, Addison disease

25
Q

DR4

A

Rheumatoid arthritis, diabetes mellitus type 1,

Addison disease

26
Q

DR5

A

Hashimoto is an odd doctor (DR3, DR5):

Hashimoto thyroiditis

27
Q

Rule of 8:

A

MHC II × CD4 = 8; MHC I × CD8 = 8.

28
Q

Differentiation of T cells

Positive selection

A

Thymic cortex. T cells expressing TCRs capable of binding self-MHC on cortical epithelial cells survive.

29
Q

Negative selection

A

Thymic medulla. T cells expressing TCRs with high affinity for self antigens undergo apoptosis or
become regulatory T cells.

Tissue-restricted self-antigens are expressed in the thymus due to the action of autoimmune regulator (AIRE); deficiency leads to autoimmune polyendocrine syndrome.

30
Q

Th1 cell

  • Secretes
  • Function
  • Induced by
  • Supressed by
  • Immunodeficency
A

IFN-γ
Activates macrophages and cytotoxic T cells
IFN-γ, IL-12
IL-4, IL-10
Mendelian susceptibility to mycobacterial disease

31
Q

Th2 cell

  • Secretes
  • Function
  • Induced by
  • Supressed by
A

IL-4, IL-5, IL-6, IL-10, IL-13
Activate eosinophils and promote production of IgE.
IL-2, IL-4
IFN-γ

32
Q

Th17 cell

  • Secretes
  • Function
  • Induced by
  • Supressed by
  • Immunodeficency
A 
IL-17, IL-21, IL-22
Immunity against extracellular microbes, neutrophil.
TGF-β, IL-1, IL-6
IFN-γ, IL-4
Hyper-IgE syndrome
33
Q

ThReg cell

  • Secretes
  • Function
  • Induced by
  • Supressed by
  • Immunodeficency
A 
TGF-ß, IL-10, IL-35
Prevent autoimmunity
TGF-β, IL-2
IL-6
IPEX
34
Q

IPEX

A

(Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked) syndrome

Genetic deficiency of FOXP3 leads to autoimmunity.

Associated with diabetes in male infants.

35
Q

T-cell activation

A

T-cell activation (signal 1): antigen is presented on MHC II and recognized by TCR on Th (CD4+) cell. Endogenous or cross-presented antigen is presented on MHC I to Tc (CD8+) cell.

Proliferation and survival (signal 2): costimulatory signal via interaction of B7 protein (CD80/86) on dendritic cell and CD28 on naïve T cell.

36
Q 
B-cell activation and
class switching
A
  1. Th-cell activation
  2. foreign antigen is presented on MHC II and recognized by TCR on Th cell.
  3. CD40 receptor on B cell binds CD40 ligand
    (CD40L) on Th cell.
4. Th cell secretes cytokines that determine
Ig class switching of B cell.

USMLE 1 (73 decks)

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