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*USMLE Step 1, General Principles > Immunology > Flashcards

Immunology Flashcards

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USMLE® Step 1 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
Q 
MHC class I
- HLA types (3)
A

HLA-A, HLA-B, HLA-C

26
Q 
MHC class II
- HLA types (3)
A

HLA-DP, HLA-DQ, HLA-DR

27
Q

Cells that express MHC class I molecules

A

All nucleated cells + platelets

NOT RBCs

28
Q

Cells that express MHC class II molecules

A

APCs

29
Q

MHC class I molecules present ___ synthesized antigens to ___ T cells

A

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
Q

MHC class II molecules present ___ synthesized antigens to ___ T cells

A

Exogenously synthesized antigens to CD4+ T cells

Bacterial antigens

31
Q

Antigen loading onto MHC class I molecules

A

Antigenic peptide fragments translocated via transporter (TAP complex) into rER where loaded onto MHC I

32
Q

Antigen loading onto MHC class II molecules

A

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
Q

Unique protein a/w MHC I

A

Beta-2 microglobulin, which directs MHC I transport to cell surface

34
Q

Unique protein a/w MHC II

A

Invariant chain, which inhibits binding of self-antigens until fusion with phagolysosome containing antigenic peptides

35
Q

Unique NK cell marker

A

CD56+

36
Q

NK cell marker that functions in ADCC

A

CD16+ = membrane receptor for Fc region of IgG

37
Q

NK cells target tumor cells and virally-infected cells with

A

Decreased/absent MHC class I expression

38
Q

NK cells employ 2 receptor types critical for their cytotoxic function

A

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
Q

Cytokines (4) that activate NK cells

- Cytokines and source

A

Virally infected cells: IFN-alpha, IFN-beta
T cells: IL-2
Macrophages: IL-12

40
Q

B cell receptor

  • # idiotypes per cell
  • # isotypes per cell
  • # antigen-binding sites
A

Idiotype = Antigen-binding site

1 idiotype
2 isotypes (IgM, IgG)
2 antigen-binding sites (valence = 2)
41
Q

T cell receptor

  • # idiotypes per cell
  • # isotypes per cell
  • # antigen-binding sites
A

Idiotype = Antigen-binding site

1 idiotype
1 isotype (α/β)
1 antigen-binding site (valence = 1)
42
Q

B cell receptor

- Glycoprotein components

A

Heavy chain (2) + light chain (2)

43
Q

T cell receptor

- Glycoprotein components

A

α chain + β chain

44
Q

B cell receptor

- Components of signal transduction complex

A

Igα, Igβ, CD19, CD21

45
Q

T cell receptor

- Components of signal transduction complex

A

CD3

46
Q

T cell development

- Differentiation/development that occurs in the subcapsular zone of the thymus (2)

A

(1) Beta-gene rearrangement (TCR)
(2) Co-expression of CD4 and CD8

Double negative –> Double positive

47
Q

T cell development

- Differentiation/development that occurs in the cortex (2)

A

(1) Alpha-gene rearrangement (TCR)
- -> Functional alpha/beta TCR
(2) Positive selection

48
Q

Positive selection

A

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
Q

T cell development

- Differentiation/development that occurs in the medulla (1)

A

Negative selection

50
Q

Negative selection

A

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
Q

Central tolerance

A

Tolerance = Immunologic unresponsiveness to self antigens

CENTRAL TOLERANCE acquired in the thymic medulla during negative selection

52
Q

Peripheral tolerance

A

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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