Stephanie was studying for her final exams this past fall. She woke up on the mo

Question

Stephanie was studying for her final exams this past fall. She woke up on the morning of her human biology exam day feeling ill. She had chills, severe body aches, a fever and felt totally exhausted. She went to the doctor hoping that antibiotics might help her feel better and get her through her exams. The doctor said that she had the flu. In addition to the antibiotic prescription, he also suggested she drink plenty of fluids and get lots of rest. The doctor also questioned whether Stephanie was given any vaccines in the last year and suggested she get one this year. Stephanie did not feel better about 5 days later and then was diagnosed with pneumonia.

1. Explain what antigenic shift is and its importance.

2. Did the antibiotics help Stephanie’s flu get better? Explain.

3. Is a vaccine a type of passive or active immunity? Explain.

4. In what form would a T cell recognize this virus?

5. Is this a primary or secondary immune response? How can you tell? Think about what happens in each of these responses.

6. Now that Stephanie has immunity to this specific virus, what is the basis of this immunity?

Explanation / Answer

1) Antigenic shift is the genetic change which occurs in infectious agents (like Viruses) resulting in a change in their surface antigens due to combination between different strains of a virus or strains of two or more viruses. It occurs because the genome of the viruses are segmented allowing for a type of genetic exchange by reassortment. Antigenic shift happens only ocassionally ( after every few years). One of the best example in which antigenic shift occurs is Influnza type A viruses which experiences changes every 10 years.

Antigenic shift is an important biological phenomenon for the emergance of new viral pathogens as its is a pathway that the virus use to find new host.Our immune system uses memory as one of the main stragtey to ward off pathogens by developing antibodies against that specific pathogens and remembering that specific pathogens in case of recurrance. However, antigenic shift changes the surface antigen structure of the pathogens so that antibodies are not able to recognise the pathogens and are not able to mount and attack quickly. Antigenic shift rendering the memory based identification of pathogens by antibodies useless. Therefore, Antigenic shift is of improtance in understanding and studying the pathogens and the disease they cause.

2) No the antibiotics did not help Stephanie get better. Pneumonia can be caused by viruse, bacteria or fungi although the latter causes less commonly. Since eventhough Stephanie took antibiotics and did not fill better, the Pneumonia was probably caused by a viruse because antibiotics can only kill or inhibit bacterias preventing infections.

3) A vaccine can be of both type, active and passive immunity. When a vaccine is use to activate our bodies immune system by the production of antibodies that can fight off pathogens then it is active immunity. But when antiboties taken from a donor are directly injected into an induvidual against a particular pathogen it is called passive immunity. Active immunity is longer effect then passive immunity.

4) T cells can of two types helper T cells and Cytotoxic T cells. Cytotoxic T cells are able to identify and kill viruse infected cells directly.

5) It is a primary immune response because Stephanie was not getting better even after 5 days which means her immune system was taking time to recognize the antigen and how to make the antiboties against it and eventually memory B cells. If It where a secondary response it would have taken much less time for the immune system to recognize and act against the antigen.

6) Her antibodies will be able to recognize this specific viruse on the basis of its surface antigenic proteins if it changes due to antigenic shift the antibodies will not be able to recognize it.

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