Type IV Hypersensitivity Flashcards
Was first described in 1890 by Robert Koch. Sensitized T cells, rather than antibodies, play the major role in its manifestations
Type IV Hypersensitivity
Type IV Hypersensitivity is also known as
Delayed hypersensitivity
He observed that individuals infected with _ developed a localized inflammatory response after receiving intradermal injections of a filtrate from the organism
Mycobacterium tuberculosis (Mtb)
Induce hematopoiesis of cells of the granulocyte-macrophage lineage and chemokines such as monocyte chemotactic protein (MCP-1/CCL2) recruit macrophages to the site.
IL3 and GM-CSF
In the tissues, the monocytes differentiate into macrophages and are activated by
IFN-γ and TNF-β
Chronic persistence of antigen leads to the development of organized clusters of cells are called
Granulomas
Granulomas are consists of
Epithelioid-shaped and multinucleated fused macrophages with an infiltrate of lymphocytes or other WBCs
Type of antigen that can be bacteria, fungi, parasites, or viruses.
Intracellular pathogens
Examples of intracellular pathogens
Mycobacterium tuberculosis, Mycobacterium leprae, Pneumocystis carinii, Leishmania species, and herpes simplex virus
Type of antigens that can come into direct contact with skin
Plants such as poison ivy and poison oak, metals such as nickel salts, and components of hair dyes and cosmetics
The most common causes of contact dermatitis
Poison ivy, poison oak, and poison sumac
This chemical is release in the plant sap and leaves
Urushiol
Caused by contact with these plants affects millions of Americans every year.
Allergic dermatitis
Other common compounds that produce allergic skin manifestations include
nickel; rubber; formaldehyde; hair dyes and fabric finishes; cosmetics; and medications applied to the skin, such as topical anesthetics, antiseptics, and antibiotics
Cytokine production by the Th1 cells causes
Macrophages to accumulate and release cytokines and other substances that produce a local inflammatory response
Produces a skin eruption characterized by erythema, swelling, and the formation of papules that appears from 6 hours to several days after the exposure
Contact dermatitis
Is mediated predominantly by sensitized T lymphocytes that respond to inhaled allergens.
Hypersensitivity pneumonitis
Other names for hypersensitivity pneumonitis
Farmer’s lung, bird breeder’s lung disease, and humidifier or air conditioner lung disease
Bacterial and fungal spores, which individuals are exposed to from working with moldy hay, pigeon droppings, compost, moldy tobacco, infested flour, and moldy cheese
Causes hypersensitivity pneumonitis
Used clinically to detect delayed hypersensitivity responses to a variety of antigens. The tests are based on a T-cell–mediated memory response.
Skin testing
Used to determine allergen sensitivity in contact dermatitis, to assess exposure to Mycobacterium tuberculosis, and to evaluate competency of cell-mediated immune responses in patients with immune deficiency diseases.
Skin testing
The gold standard in testing for contact dermatitis.
Patch test
Redness with papules or tiny blisters is considered a
Positive test
The tuberculin skin test that uses an M tuberculosis antigen extract prepared from a purified filtrate of the organism’s cell wall is called
Purified protein derivative (PPD)
Induration reaction of 15 mm or more is considered
Positive test in individuals with no risk factors
Reaction of 10 mm or greater is considered
Positive in recent immigrants of high prevalence countries
An induration reaction of 5 mm or more is considered
Positive in persons who have HIV infection or other forms of immunosuppression
Antigens typically used for testing are from sources to which individuals have been commonly exposed such as
C. albicans, tetanus toxoid, Streptococcus bacteria and fungal antigens like trichophyton and histoplasmin
