Question 1

Patients with this disease are at greater risk for fungal infections than patients with other phagocytosis-related deficiencies:&#10;A) Gaucher's disease&#10;B) Myeloperoxidase deficiency&#10;C) Chronic granulomatous disease&#10;D) Complement receptor deficiency

Accepted Answer

Patients with myeloperoxidase deficiency can usually kill bacteria with oxygen-independent mechanisms, but fungi are more difficult to kill in this manner, so fungal infections can be a serious problem for these patients.

Question 2

Why is enzyme replacement therapy with imiglucerase an effective treatment for some forms of Gaucher's disease?&#10;A) Imiglucerase breaks down glucocerebroside.&#10;B) Imiglucerase regenerates deficient myeloperoxidase.&#10;C) Imiglucerase facilitates the production of active cytochromes.&#10;D) Imiglucerase breaks down fungi when the body is not able to.

Accepted Answer

Imiglucerase is a glucocerebrosidase, which breaks down glucocerebroside that has built up in the cell. Patients with Gaucher's disease lack this enzyme and during the intracellular degradation of aged and senescent red blood cells, glucocerebroside builds up in the phagocytes. This build-up leads to a reduction in protein kinase C activity that is necessary for macrophage activation. The reduced macrophage activity leads to a variety of symptoms in patients, including the potential for seizures or pancytopenia. Imiglucerase helps protect the patient against these harmful ramifications of the disease.

Question 3

Some bacteria can avoid oxygen-dependent phagocytic killing by producing:&#10;A) Catalase&#10;B) Defensins&#10;C) Singlet oxygen&#10;D) Superoxide dismutase

Accepted Answer

Some bacteria are able to produce catalase or peroxidase, which can break down hydrogen peroxide. By breaking down hydrogen peroxide, the bacteria are able to defend themselves against the damaging effects of the phagocyte, and may be able to survive within the phagolysosome and potentially replicate inside the host immune cell.

Question 4

Which is a key component in oxygen-independent phagocytic killing?&#10;A) Lysozyme&#10;B) Myeloperoxidase&#10;C) Hypochlorous acid&#10;D) Superoxide dismutase

Accepted Answer

Lysozyme (along with defensins, lactoferrin and others) is an enzyme involved in oxygen-independent phagocytic killing. Lysozyme destroys the bacterial cell wall. Myeloperoxidase, hypochlorous acid, and superoxide dismutase are all mechanisms that use oxygen-containing components to create molecules that damage bacteria.

Question 5

Following phagocytic ingestion of a pathogen, which of the following occurs?&#10;A) Pinocytosis&#10;B) Phagosome fusion with granules&#10;C) Binding to antibody by Fc receptor on phagocyte&#10;D) Binding to complement fragments by complement receptors

Accepted Answer

After phagocytic ingestion of a pathogen, which is a separate process from pinocytosis, the phagosome fuses with primary, secondary, and tertiary granules. These granules contain a variety of chemicals that participate in oxygen-independent killing of the pathogen. Complement receptor and Fc receptor binding takes place prior to ingestion of the pathogen.

Question 6

What is the purpose of complement receptor binding to complement fragments during phagocytosis?&#10;A) Reduces production of ATP&#10;B) Causes production of catalase&#10;C) Triggers production of superoxide&#10;D) Facilitates internalization of pathogen

Accepted Answer

Complement fragments coat the surface of the pathogen, and complement receptors on the surface of phagocytes bind to the fragments. The complement components act as an opsonin, facilitating a strong bond between the phagocyte and the pathogen and allowing the phagocyte to internalize the microbe. Engagement of complement receptors does not directly affect the production of ATP, catalase, or superoxide.

Deck 12: Phagocytosis and Intracellular Killing