chronic inflammation

Question 1

What cells are characteristic of chronic inflammation?

Answer 1

Lymphocytes and plasma cells.

Question 2

How does chronic inflammation differ from acute inflammation?

Answer 2

Chronic inflammation is a delayed response but more specific, involving adaptive immunity.

Question 3

What are the common stimuli for chronic inflammation?

Answer 3

Persistent infections (most common cause).
Infections with viruses, mycobacteria, parasites, and fungi.
Autoimmune diseases.
Foreign material.
Certain cancers

Question 4

Where are T lymphocytes produced and developed?

Answer 4

Produced in the bone marrow as progenitor T cells.
Develop in the thymus, where TCR undergoes rearrangement

Question 5

What do progenitor T cells differentiate into in the thymus?

Answer 5

CD4+ helper T cells.
CD8+ cytotoxic T cells.

Question 6

What complex do T cells use for antigen surveillance?

Answer 6

The TCR complex, which includes:

TCR (T-cell receptor).
CD3.

Question 7

What does the TCR complex recognize?

Answer 7

Antigen presented on MHC molecules.

CD4+ T cells: MHC Class II.
CD8+ T cells: MHC Class I.

Question 8

What two signals are required for T-cell activation?

Answer 8

Binding of antigen/MHC complex.
A second activation signal.

Question 9

How are CD4+ helper T cells activated?

Answer 9

1.Antigen Presentation: Extracellular antigen is phagocytosed, processed, and presented on MHC class II by APCs.

2.Second Signal: B7 on APC binds CD28 on CD4+ T cells

Question 10

What are the two subsets of activated CD4+ T cells, and their cytokines?

Answer 10

TH1 subset:
Secretes IFN-γ: Activates macrophages, promotes B-cell switching to IgG, supports TH1 phenotype, inhibits TH2 phenotype.

TH2 subset:
Secretes IL-4 (IgE class switching), IL-5 (eosinophil activation and IgA class switching), and IL-13 (similar to IL-4).

Question 11

How are CD8+ cytotoxic T cells activated?

Answer 11

Antigen Presentation: Intracellular antigen is presented on MHC class I by nucleated cells and platelets.

Second Signal: IL-2 from CD4+ TH1 cells.

Question 12

What are the two mechanisms of CD8+ cytotoxic T-cell killing?

Answer 12

Perforin and granzyme secretion: Perforin creates pores for granzyme to enter, inducing apoptosis.

FasL expression: FasL binds Fas on target cells, activating apoptosis.

Question 13

How are immature B cells matured?

Answer 13

They undergo immunoglobulin rearrangement in the bone marrow to become naïve B cells expressing surface IgM and IgD.

Question 14

What are the two pathways for B-cell activation?

Answer 14

Antigen Binding: Surface IgM or IgD binds antigen, leading to maturation into IgM- or IgD-secreting plasma cells.

Antigen Presentation to CD4+ T Cells:
CD40 receptor on B cell binds CD40L on helper T cell (2nd signal).
Helper T cells secrete IL-4 and IL-5, mediating isotype switching, hypermutation, and plasma cell maturation.

Question 15

What characterizes granulomatous inflammation ?

Answer 15

A granuloma: A collection of epithelioid histiocytes (macrophages with abundant pink cytoplasm), surrounded by giant cells and a rim of lymphocytes

Question 16

What are the two subtypes of granulomas, and their characteristics?

Answer 16

Noncaseating Granulomas: Lack central necrosis.
Seen in sarcoidosis, beryllium exposure, Crohn disease, cat scratch disease, and foreign material reactions.

Caseating Granulomas: Have central necrosis.
Seen in tuberculosis and fungal infections

Question 17

How do macrophages present antigen to CD4+ helper T cells?

Answer 17

Macrophages process and present antigen via MHC class II to CD4+ helper T cells.

Question 18

What does the interaction between macrophages and CD4+ helper T cells induce?

Answer 18

It induces macrophages to secrete IL-12, which drives CD4+ helper T cells to differentiate into the TH1 subtype.

Question 19

What do TH1 cells secrete, and what is the effect on macrophages?

Answer 19

TH1 cells secrete IFN-γ, which converts macrophages into epithelioid histiocytes and giant cells.