Type IV: Hypersensitivity

Question 1

What is granulomatous inflammation characterized by? What is caused by?

Answer 1

collections of activated macrophages and T cells

strong activation of T cells leading to macrophage activation and injury to normal tissues

(strong TH1 activation and high production of cytokines (IFNy)

Question 2

What are the two types of granulomas?

Answer 2

foreign body granulomas: incited by intert foregin bodies in absence of T cell mediated immune responses

immune granulomas: agents incite strong T cell mediated immune response, macrophages activate T cells to produce cytokines IFNy activates macrophages, IL-2 activates other T cells

Question 3

What type of granuloma is associated with Type IV hypersensitivity?

Answer 3

immune granuloma

T-cell mediated disease

Question 4

What are some diseases associated with granulomatous inflammation?

Answer 4

tuberculosis, leprosy, syphilis, cat scratch disease, sarcoidosis, crohn’s disease

Question 5

Hypersensitivity reactions are often associated with inheritance of what genes?

Answer 5

HLA and non-HLA

Question 6

Why is tuberculosis associated with the type of necrosis it is associated with?

Answer 6

caseated necrosis:

because TB leads to granuloma, huge fused macrophage conglomerate

and the middle of this will die, no oxygen and damage…so necrosis

Question 7

Which types of T cells are responsible for Type IV reactions?

Answer 7

Th1: activate macrophages
Th17: enhance neutrophils, promote barrier integrity
CTLs: kill virus infected cells

Question 8

For a Type IV reaction to occur what is the prerequisite

Answer 8

first, an infection or immunization sensitizes the individual

Question 9

How does the PPD test rely on Type IV reactions?

Answer 9

Test for tuberculosis
you add the antigen, wait for a inflammation response that is sensitized only if they have been exposed to tuberculosis before

Question 10

Patients with genetic deficiencies in making which cytokines (or receptors for them) are vulnerable to severe mycobacterial infection. Why?

Answer 10

IL-12
IFNy

the macrophage must release IL-12 to induce Th1 response, which then results in IFNy,

this is all necessary for macrophage activation, monocyte recruitment (TNF release), etc.

Question 11

Difference between primary and secondary tuberculosis?

Answer 11

Primary tuberculosis: seen as an initial infection, usually in children. The initial focus of infection is a small subpleural granuloma accompanied by granulomatous hilar lymph node infection. Together, these make up the Ghon complex. In nearly all cases, these granulomas resolve and there is no further spread of the infection.
Secondary tuberculosis: seen mostly in adults as a reactivation of previous infection (or reinfection), particularly when health status declines. The granulomatous inflammation is much more florid and widespread. Typically, the upper lung lobes are most affected, and cavitation can occur.

http://library.med.utah.edu/WebPath/TUTORIAL/MTB/MTB.html