Solutions microbiology set 3-26

SOLUTIONS

Which of the following structures is responsible for the changes in influenza viruses that requires the development of a new vaccine each season?

1. Changes in the envelope phospholipids
2. Changes in the internal capsid proteins
3. Changes in the surface spike proteins
4. Changes in the DNA genome
5. All of the above

Answer

• c. Changes in the surface spike proteins

Explanation:

Influenza virus contains RNA and not DNA, and its genome encodes four major structures which are the spike protein, nucleocapsid protein, membrane protein and the envelope protein. The most important part of the virus is the spike proteins which are HA (hemagglutinin) and NA (neuraminidase). These two proteins keep changing due to changes in the genome resulting to what is called antigenic drift. The two spike proteins are the target for cell receptors and are used as the target for vaccine. Thus, any change in the genome will result to change in these spike proteins structure, and hence new vaccine is needed after every change

Question:

.  Which of the following best describes the innate immune system?

1. a targeted and highly specific response to a single pathogen or molecule
2. a generalized and nonspecific set of defenses against a class or group of pathogens
3. a set of barrier mechanisms that adapts to specific pathogens after repeated exposure
4. the production of antibody molecules against pathogens

Answer

• b. a generalized and nonspecific set of defenses against a class or group of pathogens

Explanation:

Innate immune system is nonspecific and which comes to play immediately when an antigen is introduced into the body. Mechanisms involved in innate immunity includes skin structure and cells that prevent entry of pathogens, chemicals in the blood such as chemokines and cytokines, and the immune system cells like T cytotoxic cells that attack the infected and foreign cells.

Question:

Which of the following is a characteristic of the adaptive immune response and not of the innate immune response?

1. Clonal expansions of activated B cells
2. Physical and chemical barriers
3. Inflammatory mediators
4. Phagocytosis

 Answer

• a. Clonal expansions of activated B cells

Explanation:

B cell activation involves two process; differentiation and clonal expansion. When the B cell receptor attaches on the cell surface of the antigen in the body, the B cell proliferates and secretes a free receptor form which is called antibody, which possesses the same binding pattern as those on the original cell surface. Clonal expansion involves migration to the germinal centers especially when B cell activation occurs in the lymph node. In clonal expansion, the daughter cells arise from a parent cell and after an antigen has been identified by the B cells, it can make several copies with specificity for the same antigen which is the main characteristic of adaptive immunity.

Question:

The effects of endotoxin and exotoxins are mechanisms by which bacteria can cause disease. Exotoxins are generally more potent than endotoxin because unlike endotoxin,

1. many act as catalysts and are reusable
2. they have a higher specificity of action
3. they can act at distant sites in the host
4. all of the above

Answer

• d. all of the above

Explanation:

Exotoxins resemble enzymes in various ways including the fact that they are denatured by heat, acid, proteolytic enzymes, they are proteins, and have a high biological activity as well as specificity of action which is not a feature of endotoxins. Exotoxins are secreted by both gram positive and gram negative bacteria, and due to the fact that they are secreted in high amounts and in most bacteria compared to endotoxins, they can act at a site that is distant from the infectious site.