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Immunology > Immunology > Flashcards

Immunology Flashcards

1
Q

Lymph node- role

A

Many afferents + 1 or more efferents

Role: non-specific filtration by macrophages, storage of B and T cells and immune response activation

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2
Q

Follicle

A

site of B cells (localization and proliferation)

Primary follicles (dormant and dense)
Secondary follicles (active and have central pallor)
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3
Q

Paracortex

A

Houses T cells. Contains high endothelial venues through with T and B cells ENTER from the blood

Not well developed in pts with DiGeorge syndrome

Paracortex enlarges in extreme cellular immune response (e.g. viral infection)

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4
Q

Medulla

A

Medullary cords (closely packed lymphocytes and plasma cells) and medullary sinuses.

Medullary sinuses communicate with efferent lymphatics and contain reticular cells (fibroblasts that produce collage) and macrophages

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5
Q

Cervical

A

Head and neck

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6
Q

Hilar

A

Lungs

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7
Q

Mediastinal

A

Trachea and esophagus

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8
Q

Axillary

A

Upper limb, breast, skin above umbilicus

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9
Q

Celiac

A

Liver, stomach, spleen, pancreas, and upper duodenum

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10
Q

Superior mesenteric

A

Lower duodenum, jejunum, ileum, colon to splenic flexure

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11
Q

Inferior mesenteric

A

Colon from splenic flexure to upper rectum

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12
Q

Internal iliac

A 
Lower rectum to anal canal (above pectinate)
Bladder
Vagina (middle 1/3)
Cervix
Prostate
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13
Q

Para-aortic

A

Testes, ovaries, kidneys, uterus

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14
Q

Superficial inguinal

A

Anal canal (below pectinate line)
Everything (including legs) below umbilicus (except popliteal area)
Scrotum
Vulva

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15
Q

Popliteal

A

Dorsolateral foot

Posterior calf

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16
Q

Right lymphatic duct

A

Drains right side of the body above diaphragm

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17
Q

Thoracic duct

A

Drains everything into the junction of the left subclavian and internal jugular vein

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18
Q

Sinusoids of the spleen

A

Red pulp- with fenestrate (barrel hoop) basement membrane

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19
Q

Spleen- T cell location

A

found in the periarteriolar lymphatic sheet (PALS) within the white pulp

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20
Q

Spleen- B cell location

A

found in the follicles within the white pulp

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21
Q

Marginal zone

A

Between the red pulp and the white pulp

Contains macrophages and specialized B cells (where APCs capture blood-borne antigens for recognition by lymphocytes)

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22
Q

Macrophages

A

Remove encapsulated bacteria

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23
Q

Splenic dysfunction

A

E.g. post-splenectomy, sickle cell disease

Decreased IgM –> decreased complement activation –> decreased C3b opsonization –> increased susceptibility to encapsulated organisms

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24
Q

Splenic dysfunction- Susceptible Organisms

A

“Please SHINe my SKiS”

Pseudomonas A.
Strep pneumo
Hemophilus Influenzae
Neisseria meningitidis
Salmonella sp
Klebsiella pneumonia
Group B Streptococci
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25
Q

Post splenectomy cells

A

Howell-Jolly bodies (nuclear remnant- RNA)
Target cells
Thrombocytosis (loss of sequestration and removal)
Lymphocytosis (loss of sequestration)

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26
Q

Thymus

A

Located in the anterosuperior mediastinum

Site of T-cell differentiation and maturation

Thymus is derived from “Thyrd” pharyngeal pouch

Lymphocytes- mesenchymal origin

Cortex- dense with immature T cells; Medulla- pale with mature T cells and Hassall corpuscles continue epithelial reticular cells (secrete thymic hormones??)

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27
Q

T cells vs. B cells

A

T cells = Thymus

B cells = Bone marrow

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28
Q

Hypoplastic/hyperplastic thymus

A

Hypoplastic- Seen in diGeorge and SCID

Enlarged- in myasthenia gravis

29
Q

Innate immunity

A

Components: Mphages, neutrophils, monocytes, dendritic cell, NK cells, complement

Encoded by gremlin

Rapid response to pathogens, non-specific

Secretes: lysozymes, complment, C-reactive protein, defensins

Toll-like receptors: pattern recognition receptors that PAMPs (e.g. LPS (gram neg bacteria), flagellin (bacteria), nucleic acids (viruses))

30
Q

Adaptive immunity

A

Components: T cells, B cells, and circulating antibodies

Variation through VDJ recombination during lymphocyte development

Highly specific; develops over long periods (memory response is faster and more robust)

Secretes: immunoglobulins

Memory cells: activated by B and T cells; subsequent exposure to a previously encountered antigen –> stronger, quicker immune response

31
Q

MHC I and II

A

Encoded by HLA genes and present antigen fragments to T cells

32
Q

MHC class I

A

HLA- A, B and C

Bind to TCR and CD8

Expressed on ALL nucleated cells (therefore not RBCs)

Present ENDOGENOUSLY synthesized antigens (viral or cytosolic proteins) to CD8+ cytotoxic T cells

Antigen peptides loaded onto MHC I in RER after delivery via TAP (transporter associated with antigen processing)

Associated proteins: beta-2 microglobulins (3 alpha chains and 1 beta globulin)

Viral infection activate and up regulate MHC Class I molecules

33
Q

MHC class II

A

HLA DP, DQ, DR

Bind to TCR and CD4

Expressed on APCs

Present exogenously synthesized antigens (bacterial proteins) and to CD4+ helper T cells

Antigen loaded following the release of invariant chain (2 alpha and 2 beta chains) in an acidified endosome

Invariant chain is digested by Mphages during antigen processing

34
Q

HLA A3

A

Hemochromatosis

35
Q

HLA B8

A

Addison disease, myasthenia gravis

36
Q

HLA B27

A

PAIR (seronegative arthropathies): Ankylosing spondylitis, Reactive arthritis, Psoriatic arthritis, IBD associated arthritis

37
Q

HLD DQ2/DQ8

A

Celiac

38
Q

DR2

A

MS, hay fever, SLE, Goodpastures

39
Q

DR3

A

DM type I, SLE, Graves, Hashimoto thyroiditis, Addison (also B8)

40
Q

DR4

A

RA (4 walls in a rheum), DM type I, Addison (also B8 and DR3)

41
Q

DR5

A

Pernicious anemia (B12 def), Hashimoto thyroiditis

42
Q

NK cells

A

Part of the INNATE immune system

Use perforin and granzymes to INDUCE APOPTOSIS of virally infected and tumor cells

Induced to kill when exposed to a activation signal on target cell or an ABSENCE of MHC class I on target cell surface (e.g tumor cells)

Also kills via antibody-dependent cell-mediated cytotoxicity (CD16 binds Fc region of bound Ig, activating the NK cell)

43
Q

B cell functions

A

Recognize antigen (then undergo somatic hypermutation to optimize antigen specificity)

Produce antibody (differentiate into plasma cell to secrete specific Ig)

Maintain immunologic memory- memory B cells persist (for accelerated future response to antigen)

44
Q

T cell functions

A

CD4+ T cells- help B cells make antibodies and produce cytokines to recruit phagocytes and activate other leukocytes

CD8+ T cells- kill virus-infected cells

Delayed cell-mediated hypersensitivity

Acute and chronic cellular organ rejection

45
Q

Helper T cell + IL-12

A

Th1 cell

46
Q

Helper T cell + IL- 4

A

Th2 cell

47
Q

Helper T cell + TGF B + IL-6

A

Th17 cell

48
Q

Positive selection

A

Thymic CORTEX

T cell expressing TCRs capable of binding self-MHC on cortical epithelial cells survive (enough, but not too much)

49
Q

Negative selection

A

Thymic MEDULLA

T cells expressing TCTs with high affinity for self-antigens undergo apoptosis

Tissue-restricted self-antigens are expressed in the thymus due to the action of autoimmune regulator (AIRE); deficiency leads to autoimmune polyendocrine syndrome-1

50
Q

Th1 cells

A

Th1 cells- secrete IFN gamma

Activates Mphages and cytotoxic T cells

Differentiation induced by IFN-gamma and IL-12

Inhibited by IL-4 and IL-10 (from Th2 cells)

Cyclical interaction between Mphages and Th1: Mphages release IL-12 –> stimulates Th1 cell differentiation –> release IFN-gamma –> stimulates Mphages

51
Q

Th2 cells

A

Secretes IL-4, IL-5, IL-10, and IL13

Recruits eosinophils for parasite defense and promotes IgE production by B cells

Differentiation induced by IL-4

Inhibited by IFN gamma (from Th1 cells)

52
Q

Helper T cells and APCs

A

CD4 on Th cells bind to MHC Class II of APCs

53
Q

Cytotoxic T cells

A

Kill virus-infected, neoplastic, and donor graft cells (induce apoptosis)

Release cystic granules containing preformed proteins (granzymes, perforins)

54
Q

Regulatory T cells

A

Help maintain specific immune tolerance by suppressing CD4 and CD8 activity

Identified by expression of CD3, CD4, CD25, and FOXP3

Produce IL-10 and TGF B (anti-inflammatory cytokines)

55
Q

(Naive) T cell activation

A
  1. Dendritic cell samples and processes antigen
  2. Dendritic cell moves to lymph node (paracortex)
  3. Dendritic cell presents antigen on MHC Class I and Class II
  4. Two signals required for T-cell activation:
    (a) Signal 1: Exogenous antigen (on MHC Class II) is presented by APC (dendritic cell) and recognized by TCR on CD4 T helper cell; similarly endogenous antigen (on MHC Class I ) is presented by APC and recognized by TCR on CD8 cytotoxic T cell
    (b) Signal 2: Proliferation and survival; co-stimulatory signal via B7 proteins (on APC) and CD28 (on naive T cell)
  5. Th cell activates and produces cytokines, while Tc cell activates is able to recognize and kill virus-infected cell
56
Q

B-cell activation and class switching

A
  1. Th cells are activated (using the aforementioned process)
  2. B-cell receptor mediated endocytosis; B-cell presents antigen (on MHC Class II), and it is recognized by TCR on Th cell
  3. CD40 receptor on B cell then binds to CD40L (ligand) on Th cell
  4. Th cell secretes cytokines that determine Ig class-switching of B cell
  5. B cell activates and undergoes class switching, affinity maturation, and antibody production
57
Q

Type of antigen presenting cells

A

Dendritic cells (include Langerhan cells- dendritic cells of the skin)
Mphages
B lymphocytes

58
Q

Antibody structure and function

A

Fab- antigen binding; consists of variable and hyper variable regions (light chain and heavy chain)

Fc- macrophage binding; complement binding (specifically IgM and IgG)

59
Q

Antibody diversity

A

Antigen independent

Random recombination of VJ (light chain) or VDJ (heavy chain)

Random addition of nucleotides to DNA during recombination (by TdT- terminal deoxynuclotidyl transferase)

Random combo of heavy chains with light chains

60
Q

Antibody specificity

A

Somatic hypermutation and affinity maturation (variable region)

Isotype switching (constant region)- B changes from producing one type of Ig to another (e.g. IgM to IgG

61
Q

Naive B cells (mature)

A

Express IgM and IgD

Isotype switching (mediated by cytokines and CD40L)- differentiate in germinal centers of lymph nodes from B cells into plasma cells that then secrete IgG, IgE, and IgA

62
Q

IgG

A

Main antibody in secondary (delayed response) to an antigen

Most abundant isotype IN SERUM (IgA is most produced, but not in serum)

Fixes complement, crosses the placenta, opsonizes bacteria, and neutralizes bacterial toxins and viruses

63
Q

IgA

A

Prevents attachment of bacteria and viruses to mucous membranes

Monomer in circulation or dimer (with J chain when secreted)

Produced in GI tract (Peyer patches), and protects against gut infections (e.g. Giardia)

Released in secretions (tears, saliva, and mucus) and breast milk

Picks up secretory component from epithelial cells (protects Fc portion from proteases)

64
Q

IgA deficiency

A

associated recurrent upper and lower respiratory infections and GI infections

65
Q

IgM

A

Produced in the immediate response to an antigen

Fixes complement; does not cross placenta

Pentamer with J chain when secreted (valence 10)

66
Q

IgD

A

Unclear, found on surface of B cells

67
Q

IgE

A

Binds MAST CELLS and BASOPHILS; Cross lines when expose to allergen, mediating immediate (type I) HS through release of inflammatory mediators (such as histamine)

Mediates immunity to worms by activating EOSINOPHILS; antibody-depended, cell-mediated cytotoxicity (parasite invades and gets coated with IgG and IgE –> eosinophils then bind to Fc portion of IgE –> causes degranulation of eosinophil –> release major basic protein –> kills parasite

68
Q

Memory cells

A

Antigens lacking a peptide component (e.g. LPS- lipopolysaccharides) are poorly immunogenic

Antigens with a peptide component (e.g. diphtheria vaccine) undergoes class switching and immunologic memory can occur as a result of direct contact of B cells with Th cells (CD40-CD40L interaction)

Immunology (7 decks)

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