Regulation of the Immune Response Flashcards Preview

Immunology > Regulation of the Immune Response > Flashcards

Flashcards in Regulation of the Immune Response Deck (37):
1

What is immunological tolerance?

Lack of response to a specific Ag

2

What are the two major mechanisms of tolerance induction?

deletion of reactive cells, inactivation of reactive cells (anergy)

3

What is clonal deletion? Where does it occur?

elimination of autoreactive T cells in thymus caused by tight association of T cell to MHC-presented antigen

4

Why do antigens presented from self-cells induce anergy?

Most self-cells don't have B7-1 or B7-2 so Ag from them isn't costimulated, preventing self-Ag recognition.

5

What is functional deletion?

deletion of function of T helper cells, causing loss of cytotoxicity of CTL and B cell antibody formation that require help

6

What are some mechanisms of functional deletion?

deletion of T helper specificity during selection, bias for inappropriate Th1 or Th2 response from production of certain cytokines (i.e. block Th1 cells with IL-10)

7

How does a regulatory T cell bind APCs? How is it activated?

CD4+ T cell binds B7 receptor on APC with CTLA-4, which is activated by the crosslinking of CD28 molecules

8

What are the 5 mechanisms of tolerance n in T cells?

1. clonal deletion
2. clonal anergy
3. functional deletion
4. regulatory T cells
5. blocking of presentation or activation

9

What are the 3 mechanisms of tolerance in B cells?

1. clonal deletion
2. clonal anergy
3. functional deletion

10

How do B cells become anergic?

Immature B cells expressing IgM are capped when exposed to polyclonal IgM or tolerizing Ag and the IgM internalizes. In mature B cells, re-expression occurs within 1-2 days, but immature cells don't re-express surface Ig

11

How are B cells functionally deleted?

lack of T cell help for T-dependent B cells, presentation of TI-Ag in non-crosslinking form for TI Bcells

12

What affects whether an antigen induces maturity or tolerance?

form, amount or manner of presentation of the antigen

13

Is tolerance easier to induce in mature or immature cells?

Immature cells

14

How does the immunogenicity of an antigen affect induction of tolerance?

The stronger an immunogen the more stringent regime to induce tolerance

15

How does the dose affect immunogenecity of a substance?

need the optimal dose range, higher or lower doses usually induce tolerance

16

What is high dose tolerance?

very large quantity of immunogen can turn off response to it

17

What is more immunogenic: aggregated material or disaggregated material? Why?

aggregated material, clumps and aggregates stimulate APC to phagocytose the antigen

18

Tell whether each of the following routes of administration of antigen favors immune response or tolerance: subcutaneous, oral, IM, IV

immune respone: subcutaneous, IM
tolerance: oral, IV

19

What is cyclophosphamide? What lymphocytes does it work on?

immunosuppressive drug, acts on T and B cells

20

What cells mediate positive selection in the thymus? What is the cell transition at positive selection?

cortical epithelial cells, go from immature CD3- DN thymocytes to immature CD3+ DP thymocytes

21

What cells mediate negative selection in the thymus? What is the cell transition at negative selection?

dendritic cell, immature CD3+ DP thymocytes to mature CD3+ SP thymocytes

22

Why is immune regulation needed?

prevent uncontrolled proliferation of individual B or T cell clones, prevent indefinite response to one challenge to conserve resources for another

23

What is the expression pattern of Tregs?

FoxP3+ , CD25 +, CD4 +

24

What is regulatory tolerance?

T cell specific for self-Ag becomes regulatory, IL-10 and TGFb produced by Treg inhibitsother self-reactive T cells

25

What 6 diseases do Tregs have a role in controlling?

colitis, diabetes, MS, SLE, GVHD, graft rejection

26

What are mechanisms of regulation of Tregs?

direct contact with target cells, cytokine-mediated suppression of T cells

27

What type of immunity do proteins induce?

Humoral and CMI

28

Why can't polysaccharides and lipids induce CMI?

can't be presented by MHC molecules to T cells

29

What type of immune response do polysaccharides and lipds induce?

short-lived, IgM and some IgG response to capsule

30

What type of antigen can induce long-lived immunologic memory? How?

proteins/peptides via T cell activation

31

What is antigen blocking?

Ab sequesters Ag which prevents it from being recognized by other Ag-recognizing cells and thus from activating them

32

What does crosslinking of Ig and Fc receptors on the same B cell cause?

paralytic signal to the cell

33

What does crosslinking of two Igs on the same B cell cause?

proliferative signal

34

When do immune complexes augment B cell response? Which Ab type tends to enhance?

when they opsonize APCs, IgM

35

When do immune complexes inhibit B cell response? Which Ab type tends to inhibit?

when they crosslink on same B cell, IgG

36

How is Rh disease prevented?

prevent immune response by using high dose of antiRh Ab to prevent Rh+ from seeing mother's Rh- and forming immune reponse

37

What is a direct Coomb's test?

look to see if fetal RBC agglutinate when you add anti-human rabbit Ag--if yes, they are coated in maternal Ab
take maternal serum and add Rh+ RBCs and rabbit Ag---if agglutinates, if Rh+ Ab exist