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The removal of plasmids reduces virulence in which of the following organisms?

Staphylococcus aureus

What is the LD50 for the bacterial toxin tested in the example below?

25 3 3

Which of the following is not a portal of entry for pathogens?


All of hte following can occur during bacterial infection. Which would prevent all of the others?

destruction of adhesins

The ID50 for Campylobacter sp. is 500 cells; the ID50 for Cryptosporidium sp. is 100 cells. Which of the following statements is true?

crptosporidium is more virulent than Campylobacter

An encapsulated bacterium can be virulent because the capsule...

resists phagocytosis

A drug that binds to mannose on human cells would prevent

the attachment of pathogenic E. coli

The earliest smallpox vaccines were infected tissue rubbed into the skin of a healthy person. The recipient of such a vaccine usually developed a mild case of smallpox, recovered, and was immune thereafter. the most likely reason this vaccine did not kill more people is:

Skin is the wrong portal of entry for smallpox

Which of the following does not represent the same mechanism for avoiding host defenses as the others?

Surface protein genes in Neisseria gonorrhoeae mutate frequently

Which of the following statements is true?

A successful pathogen doesn't kill its host before it is transmitted

Legionella uses C3b receptors to enter monocytes. This

prevents phagocytosis

chlamydia can prevent the formation of phagolysosomes, and therefore Chlamydia can

avoid being digested

If the following are placed in the order of occurrence, which would be the third step?

Formation of a phagosome

If the following are placed in teh order of occurence, which would be the third step?

Activation of C3

A human test host can prevent a pathogen from getting enough iron by

binding iron with transferrin

A decrease in the production of C3 would result in

increased susceptibility to infection

In 1884, Eli Metchnikoff observed blood cells collected around a splinter inserted in a sea star embryo. this was the discovery of


Heliobacter pylori uses the enzyme urease to counteract a chemical defense in the human organ in which it lives. This chemical defense is

hydrochloric acid

Which of the following statements about a-IFN is not true?

it is virus-specific

Which of the following does not stimulate phagocytes?


The type of protection provided by the injection of diphtheria toxoid.

naturally acquired passive immunity

The type of protection provided by teh injection of antirabies serum

artificially acquired active immunity

The type of protection resulting from recovery from an infection

naturally acquired active immunity

A newborns immunity to yellow fever

innate resistance

Antibodies that protect the fetus and newborn


The first antibodies synthesized; especially effective against microorganisms


Antibodies that are bound to mast cells and involved in allergic reactions


Put the following in the correct sequence to elicit an antibody response: 1) TH cell recognizes B cell; 2) APC contacts antigen; 3) antigen fragment goes to surface of APC; 4) TH recognizes antigen digest adn MHC; 5) B cell proliferates


A kidney-transplant patient experienced a cytotoxic rejection of his new kidney. Place the following in order for that rejection: 1) apoptosis occurs; 2) CD8 becomes CTL 3) granzymes released; 4) MHC class I activates CD8; 5) perforin released.


Patients with Chediak-Higashi syndrome suffer from various types of cancer. These patients are most likely lacking which of the following:

B cells

Desensitization to prevent an allergic response can be accomplished by injecting small, repeated doses of

the antigen (allergen)

In vitro, recipient serum type B will agglutinate donor cells type A: while in vivo, recipeint serum type B will lyse donor cells type A. The in vivo response is due to


cytotoxic autoimmunity differs from immune complex autoimmunity in that cytotoxic reactions

do not involve complement.

Worldwide, the primary method of transmitting HIV is

heterosexual sex

Which of the following is not the cacuse of a natural immune deficiency?

immunosuppressant drugs

Which antibodies will be found naturally in teh serum of a person with blood type A, Rh+?

anti B

Localized anaphylaxis

Type I hypersensitivity

Allergic contact dermatitis

type IV hypersensitivity

Due to immune complexes

type III hypersensitivity

Reaction to an incompatible blood transfusion

type II hypersensitivity

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