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USMLE immunology > cellular components > Flashcards

cellular components Flashcards

1
Q

What are the components of innate immunity?

A

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

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2
Q

What are the components of adaptive immunity?

A

T cells, B cells, and circulating antibodies.

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3
Q

How is innate immunity encoded?

A

Germline encoded.

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4
Q

How is adaptive immunity encoded?

A

Variation through V(D)J recombination during lymphocyte development.

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5
Q

How does innate immunity respond to pathogens?

A

Nonspecific response that occurs rapidly (minutes to hours) with no memory response.

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6
Q

How does adaptive immunity respond to pathogens?

A

Highly specific, refined over time; develops over long periods, with faster and more robust memory responses.

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7
Q

What proteins are secreted in innate immunity?

A

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

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8
Q

What proteins are secreted in adaptive immunity?

A

Immunoglobulins and cytokines.

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9
Q

What are the key features of pathogen recognition in innate immunity and what are some examples ?

A

Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs), activating NF-κB.

Examples of PAMPs: LPS (gram-negative bacteria), flagellin (bacteria), nucleic acids (viruses).

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10
Q

What are the key features of pathogen recognition in adaptive immunity?

A

Memory cells (activated B and T cells) ensure stronger and quicker immune responses upon re-exposure to antigens. Responses decrease with age (immunosenescence).

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11
Q

What is immune privilege?

A

Certain organs (e.g., eye, brain, placenta, testes) have mechanisms to limit immune responses to avoid damage from inflammation. Allograft rejection is less likely in these sites.

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12
Q

What is the function of MHC molecules?

A

Present antigen fragments to T cells and bind T-cell receptors (TCRs).

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13
Q

What genes encode MHC I and MHC II?

A

MHC I: HLA-A, HLA-B, HLA-C.
MHC II: HLA-DP, HLA-DQ, HLA-DR.

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14
Q

Where are MHC I molecules expressed?

A

On all nucleated cells, antigen-presenting cells (APCs), and platelets (except RBCs).

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15
Q

Where are MHC II molecules expressed?

A

Only on antigen-presenting cells (APCs).

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16
Q

What is the function of MHC I?

A

Present endogenous antigens (e.g., viral or cytosolic proteins) to CD8+ cytotoxic T cells.

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17
Q

What is the function of MHC II?

A

Present exogenous antigens (e.g., bacterial proteins) to CD4+ helper T cells.

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18
Q

What are the associated proteins for MHC I and MHC II?

A

MHC I: β2-microglobulin.
MHC II: Invariant chain.

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19
Q

How are antigens loaded onto MHC I?

A

Antigen peptides are loaded onto MHC I in the rough endoplasmic reticulum (RER) after delivery via TAP (transporter associated with antigen processing).

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20
Q

How are antigens loaded onto MHC II?

A

Antigen loading occurs after the release of the invariant chain in an acidified endosome.

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21
Q

Which mnemonic is associated with HLA-B27 diseases?

A

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

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22
Q

What disease is associated with HLA-B57?

A

Abacavir hypersensitivity.

23
Q

What is the mnemonic for HLA-DQ2/DQ8?

A

I ate (8) too (2) much gluten at Dairy Queen. (Celiac disease)

24
Q

What diseases are associated with HLA-DR3?

A

DM type 1,
SLE,
Graves disease,
Hashimoto thyroiditis,
Addison disease.

25
Q

What diseases are associated with HLA-DR4?

A

Rheumatoid arthritis, DM type 1, Addison disease.

26
Q

What immune system do natural killer (NK) cells belong to?

A

Innate immune system.

27
Q

How do NK cells kill virally infected and tumor cells?

A

By using perforin and granzymes to induce apoptosis.
natural killer is in innate immunity
cytotoxic t cell is in adaptive immunity

28
Q

Which cytokines enhance the activity of NK cells?

A

IL-2, IL-12, IFN-α, and IFN-β.

29
Q

When are NK cells induced to kill target cells?

A

absence of an inhibitory signal such as MHC I on the target cell.

30
Q

How do NK cells perform antibody-dependent cell-mediated cytotoxicity?

A

Through CD16 binding to the Fc region of bound IgG, activating the NK cell.

31
Q

What type of immunity is mediated by B cells?

A

Humoral immunity.

32
Q

What is the role of B cells in recognizing antigens?

A

They recognize and present antigens and undergo somatic hypermutation to optimize antigen specificity.

33
Q

What do B cells differentiate into?

A

Plasma cells, which secrete specific immunoglobulins.

34
Q

What is the role of memory B cells?

A

They persist and accelerate the future response to the same antigen.

35
Q

What type of immunity is mediated by T cells?

A

Cell-mediated immunity.

36
Q

What is the function of CD4+ T cells?

A

They help B cells make antibodies and produce cytokines to recruit phagocytes and activate other leukocytes.

37
Q

What is the function of CD8+ T cells?

A

They directly kill virus-infected and tumor cells via perforin and granzymes (similar to NK cells).

38
Q

What hypersensitivity reaction is mediated by T cells?

A

Type IV hypersensitivity reaction.

39
Q

What type of organ rejection is mediated by T cells?

A

Acute and chronic cellular organ rejection.

40
Q

Where does T cell differentiation begin, and what types of precursors are involved?

A

T cell differentiation begins in the bone marrow with T-cell precursors expressing CD4+ and CD8+

41
Q

What is the role of positive selection in the thymus?

A

Positive selection occurs in the thymic cortex and ensures T cells recognize self-peptides for cooperation in immune responses. Double-positive thymocytes expressing TCRs that recognize self-peptide MHC complexes receive survival signals.

42
Q

What happens during negative selection of T cells and what gene helps regulate this process ?

A

Negative selection in the thymic medulla removes T cells that bind strongly to self-peptides, leading to apoptosis or regulatory T cell differentiation. This process is regulated by the AIRE protein

43
Q

What syndrome is caused by a deficiency of the AIRE protein?

A

Deficiency in AIRE protein leads to autoimmune polyendocrine syndrome (e.g., chronic mucocutaneous candidiasis, hypoparathyroidism, adrenal insufficiency, recurrent Candida infections).

44
Q

What is the function of Th1 cells, and which cytokines do they secrete?

A

Th1 cells secrete IFN-γ and IL-2 to activate macrophages and cytotoxic T cells.

45
Q

What cytokines are secreted by Th2 cells, and what is their function?

A

Th2 cells secrete IL-4, IL-5, IL-6, IL-10, and IL-13 to activate eosinophils and B cells.

46
Q

What role do Th17 cells play, and which cytokines do they produce?

A

Th17 cells secrete IL-17, IL-21, and IL-22, inducing neutrophilic infiltration
important for gut mucosal immunity

47
Q

What is the primary function of regulatory T (Treg) cells?

A

Treg cells prevent autoimmunity by maintaining tolerance through suppression of CD4+ and CD8+ T cell effector functions. They produce anti-inflammatory cytokines such as IL-10 and TGF-β.

48
Q

What markers identify regulatory T cells (Tregs)?

A

Tregs are identified by expression of CD3, CD4, CD25, and FOXP3.

49
Q

what D do natural killer cells express ?

A

CD16
CD56

50
Q

what are the two types of CD4 cells ?

A

Th1 and Th2

51
Q

how does the activation on T cells happen ?

A

through B7 on. AP and CD28 on t cell along with TCR MHC 2 co stimulation

52
Q

which cytokines are in favor of the formation of Th2 and which are inn the favor of the formation off Th1?

A

Th1 - IL12 , INF gamma
Th2 - IL4 and IL10

53
Q

how do CD8 cells do the killing ?

A

granzymes
perforins
granulysin
Fas ligand

USMLE immunology (12 decks)

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