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*USMLE Step 1, General Principles > Immunology > Flashcards

Immunology Flashcards

1
Q

Lymph node

- Site of B-cell localization

A

Outer cortex

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2
Q

Lymph node

  • Primary follicle
  • Secondary follicle
A

Primary follicle - Dense and dormant

Secondary follicle - Pale, germinal centers (proliferating B cells and follicular dendritic cells)

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3
Q

Lymph node

- Medullary cords: Cell types

A

B cells, plasma cells, macrophages

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4
Q

Lymph node

- Medullary sinuses: Cell types

A

Reticular cells, macrophages

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5
Q

Lymph node

- Site of T-cell localization

A

Paracortex

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6
Q

Lymph node

- Structure that is underdeveloped in Bruton (X-linked) agammaglobulinemia

A

Outer cortex - Primary/secondary follicles

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7
Q

Lymph node

- Structure that is underdeveloped in DiGeorge syndrome

A

Paracortex

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8
Q

Secondary lymph organ that initiates immune response to TISSUE-BORN antigens

A

Lymph node

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9
Q

Secondary lymph organ that initiates immune response to BLOOD-BORN antigens

A

Spleen

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10
Q

B cells

- Site of somatic hypermutation and isotype switching

A

Outer cortex of lymph nodes

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11
Q

B cells

- Site of antibody production and affinity maturation

A

White pulp of spleen

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12
Q

Spleen

- Site of B-cell localization

A

Follicles (white pulp)

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13
Q

Spleen

- Site of T-cell localization

A

Periarteriolar lymphatic sheath (PALS); white pulp

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14
Q

Clinical findings (4) post-splenectomy

A
  1. Howell-Jolly bodies (nuclear remnants)
  2. Target cells
  3. Thrombocytosis
  4. Lymphocytosis

Spleen is storage site for RBCs, platelets, and granulocytes

Splenectomy –> Loss of sequestration site for platelets (thrombocytosis) and granulocytes (lymphocytosis)

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15
Q

Encapsulated bacteria

A

SHiNE SKiS

Streptococcus pneumoniae
Haemophilus influenzae type b 
Neisseria 
E. coli 
Salmonella
Klebsiella pneumoniae 
Group B streptococci
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16
Q

Mechanism by which splenic dysfunction increases susceptibility to encapsulated organisms

A

Spleen responsible for 50% antibody production

Decreased IgM –> Decreased complement activation –> Decreased C3b –> Decreased opsonization of encapsulated bugs –> Increased susceptibility

Encapsulated bugs are resistant to phagocytosis

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17
Q

Site of immune response initiation in the spleen

A

Marginal zone

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18
Q

Embryologic origin of thymus

A

Third pharyngeal pouch (endoderm)

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19
Q

Embryologic derivation of T cells

A

Mesoderm

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20
Q

Thymic cortex

A

Dense - Immature T cells

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21
Q

Thymic medulla

A

Pale - Mature T cells

22
Q

Structure in thymic medulla believed to be site of destruction of T cells that improperly matured

A

Hassall corpuscles (“whorls” of reticular cells)

23
Q

Structure responsible for ensuring antigen-free environment in which immature T cells develop

A

Blood-thymus barrier

24
Q

MHC class I and II molecules encoded by HLA genes on chromosome ___

A

Chromosome 6

25
``` MHC class I - HLA types (3) ```
HLA-A, HLA-B, HLA-C
26
``` MHC class II - HLA types (3) ```
HLA-DP, HLA-DQ, HLA-DR
27
Cells that express MHC class I molecules
All nucleated cells + platelets | NOT RBCs
28
Cells that express MHC class II molecules
APCs
29
MHC class I molecules present ___ synthesized antigens to ___ T cells
Endogenously synthesized antigens to CD8+ cytotoxic T cells Self antigens, tumor antigens, viral antigens Virus uses host cell machinery to translate proteins, which eventually are degraded by proteasomes and loaded onto MHC I
30
MHC class II molecules present ___ synthesized antigens to ___ T cells
Exogenously synthesized antigens to CD4+ T cells Bacterial antigens
31
Antigen loading onto MHC class I molecules
Antigenic peptide fragments translocated via transporter (TAP complex) into rER where loaded onto MHC I
32
Antigen loading onto MHC class II molecules
Transport vesicle carrying MHC II fuses with phago- or endolysosome carrying antigenic peptides Acidic environment displaces invariant chain from binding site on MHC II and permits antigen binding
33
Unique protein a/w MHC I
Beta-2 microglobulin, which directs MHC I transport to cell surface
34
Unique protein a/w MHC II
Invariant chain, which inhibits binding of self-antigens until fusion with phagolysosome containing antigenic peptides
35
Unique NK cell marker
CD56+
36
NK cell marker that functions in ADCC
CD16+ = membrane receptor for Fc region of IgG
37
NK cells target tumor cells and virally-infected cells with
Decreased/absent MHC class I expression
38
NK cells employ 2 receptor types critical for their cytotoxic function
One delivers a stimulatory (kill) signal One delivers an inhibitory (don't kill) signal Inhibitory signal binds MHC class I Tumor cells and virally-infected cells that lack MHC class I expression receive only the stimulatory (kill) signal
39
Cytokines (4) that activate NK cells | - Cytokines and source
Virally infected cells: IFN-alpha, IFN-beta T cells: IL-2 Macrophages: IL-12
40
B cell receptor - # idiotypes per cell - # isotypes per cell - # antigen-binding sites
Idiotype = Antigen-binding site ``` 1 idiotype 2 isotypes (IgM, IgG) 2 antigen-binding sites (valence = 2) ```
41
T cell receptor - # idiotypes per cell - # isotypes per cell - # antigen-binding sites
Idiotype = Antigen-binding site ``` 1 idiotype 1 isotype (α/β) 1 antigen-binding site (valence = 1) ```
42
B cell receptor | - Glycoprotein components
Heavy chain (2) + light chain (2)
43
T cell receptor | - Glycoprotein components
α chain + β chain
44
B cell receptor | - Components of signal transduction complex
Igα, Igβ, CD19, CD21
45
T cell receptor | - Components of signal transduction complex
CD3
46
T cell development | - Differentiation/development that occurs in the subcapsular zone of the thymus (2)
(1) Beta-gene rearrangement (TCR) (2) Co-expression of CD4 and CD8 Double negative --> Double positive
47
T cell development | - Differentiation/development that occurs in the cortex (2)
(1) Alpha-gene rearrangement (TCR) - -> Functional alpha/beta TCR (2) Positive selection
48
Positive selection
Cortical epithelial cells (thymus) express self MHC antigens that interact with TCR of immature thymocytes in CORTEX Able to bind self MHC --> Positive selection Unable to bind self MHC --> Failure of positive selection --> Apoptosis
49
T cell development | - Differentiation/development that occurs in the medulla (1)
Negative selection
50
Negative selection
Medullary epithelial and dendritic cells (thymus) express self MHC antigens that interact with TCR of immature thymocytes in MEDULLA Bind self MHC too strongly --> APOPTOSIS
51
Central tolerance
Tolerance = Immunologic unresponsiveness to self antigens CENTRAL TOLERANCE acquired in the thymic medulla during negative selection
52
Peripheral tolerance
Tolerance = Immunologic unresponsiveness to self antigens PERIPHERAL TOLERANCE develops by T CELL ANERGY, which is the functional inactivation of T cells that react to self antigen

*USMLE Step 1, General Principles (3 decks)

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