Immunology review and Hypersensitivity reactions

Question 1

Humoral immunity

Answer 1

Protects against extracellular microbes and toxins.

Part of adaptive immune system.

Question 2

Intracellular immunity

Answer 2

Protects against intracellular microbes and tumor cells.

Part of adaptive immune system.

Question 3

Generative lymphoid organs (primary or central)

Answer 3

sites where T and B lymphocytes mature and become competent to respond to antigens (thymus for T lymphocytes, bone marrow for B lymphocytes)

Question 4

Peripheral lymphoid organs (secondary)

Answer 4

Sites where the adaptive immune response is initiated (lymph nodes, spleen, mucosal and cutaneous lymphoid tissues (GI tract, respiratory tract, skin).

Question 5

Reactive follicular hyperplasia

Answer 5

• Germinal center develops in follicle and becomes hyperplastic
• Occurs when B lymphocytes respond to an antigen.

Question 6

MHC function

Answer 6

The physiologic function of MHC molecules is to display peptide fragments of proteins for recognition by antigen specific T cells.

Question 7

MHC gene location

Answer 7

In humans the MHC complex genes are found on chromosome 6 and are also known as the human leukocyte antigen (HLA) complex as they were initially detected on leukocytes.

Question 8

Where are MHC gene products found?

Answer 8

All mature cells except RBCs

Question 9

Class I MHC molecules

Answer 9

Coded by HLA-A, HLA-B, and HLA-C genes; display antigens that are recognized by CD8+ T-lymphocytes and NK cells

Question 10

Class II MHC molecules

Answer 10

Coded by HLA-DP, HLA-DQ, and HLA-DR genes; display antigens that are recognized by CD4+ T lymphocytes

Question 11

Uses of HLA testing

Answer 11

• Can be used to determine disease risk

- Used in transplantation work-up

Question 12

Light chain restriction

Answer 12

Kappa or Lamda typein B cells. Ig light chian expressed by neoplastic, monoclonal B cell population.

Question 13

Ways to detect light chain restriction

Answer 13

• Flow cytometry
• Serum protein electrophoresis with immunofixation electrophoresis
• Kappa and lamda in situ hybridization study

Question 14

Flow cytometry

Answer 14

-performed on fresh and unfixed tissue, blood, or body fluids.

Question 15

Can exogenous or endogenous self-antigens elicit a hypersensitivity reaction?

Answer 15

Both

Question 16

What usually causes a hypersensitivity reaction

Answer 16

Imbalance between the effector mechanisms of immune responses and the control mechanisms that serve to normally limit such responses. Often associated w/inheritance of particular susceptibility genes (HLA an non-HLA genes)

Question 17

What is the problem with hypersensitivity?

Answer 17

The reactions are poorly controlled, excessive, or misdirected.

Question 18

Immediate (Type 1) hypersensitivity reaction

Answer 18

• IgE mediated activation of mast cells with degranulation and release of mast cell contents.
• first step: sensitization
• repeat exposure causes mast cell degranulation
• Late phase reaction occurs when activated eosinophils secrete major basic protein and eosinophil cationic protein (toxic to epithelial cells) and activate mast cells to release mediators

Question 19

Antibody-mediated (type II) hypersensitivity

Answer 19

-Caused by Ab that react with normal or altered cell surface antigens in the extracellular matrix

Question 20

Atopy

Answer 20

Predisposition to develop immediate hypersensitivity reactions

Question 21

Hygiene hypothesis

Answer 21

Postulation that improved hygiene has diminished exposure to microbial antigens in early life that “educate” the immune system, setting stage for pathologic allergic responses later in life.

Question 22

Goodpasture syndrome

Answer 22

Circulating autoantibodies to antigens intrinsic to the glomerular basement membrane results in antibody mediated injury. Resulting anti-GBM immune complexes can be visualized with immunoflourescence microscopy as a linear pattern of deposition.

Question 23

Pemphigus vulgaris

Answer 23

Due to antibodies directed against desmogleins 1 and 3 (found in the desmosome)

Question 24

Immune complex mediated hypersensitivity (type 3) Steps

Answer 24

Immune complex formation
Immune complex deposition
Immune complex-mediated inflammation and tissue injury

Question 25

T cell mediated (Type IV) hypersensitivity

Answer 25

Caused by inflammation resulting from cytokines produced by CD4_ T lymphocytes and cell killing by CD8+ lymphocytes. Sensitized to exogenous or endogenous antigens

Question 26

2 mechanisms of type IV hypersensitivity

Answer 26

CD4+ T cell mediated inflammation. CD8+ T cell mediated immunity.

Question 27

CD4+ T cell-mediated inflammation

Answer 27

Response to repeat exposure of antigen, CD4+ cells secrete cytoines and cause recruitment and activation of macrophages and neutrophils causing an inflammatory response that can cause tissue injury

Question 28

Example of CD4+ T cell-mediated inflammation

Answer 28

Delayed-type hypersensitivity reaction. (Tissue reaction to antigens given to immune individuals)

Question 29

CD8+ T cell mediated immunity

Answer 29

CD8+ cytotoxic T cells kill antigen expressing target cells

Question 30

Granulomatous Inflammaiton

Answer 30

Distinctive patern of chronic inflammation. Usually results from a strong activation of T lymphocytes, leading to activated macrophages and causing tissue injury

Question 31

Granuloma

Answer 31

Focus of chronic inflammation consisting of microscopic aggregation of macrophages transformed into epithelial-like cells (histiocytes).

Question 32

What can histiocytes fuse to form?

Answer 32

Multi-nucleated giant cells

Question 33

What are granuloms the result of?

Answer 33

Immune reaction or a reaction to a foreign material

Question 34

Foreign body granulomas

Answer 34

See foreign material within histiocytes/giant cells.

Question 35

Caseating granulomas

Answer 35

Induce cell-mediated immune response w/central necrosis. Usually associated with infection