In a phenomenon known as antigenic drift, the surface proteins of influenza viru
ID: 54438 • Letter: I
Question
In a phenomenon known as antigenic drift, the surface proteins of influenza virus gradually change from year to year because of mutations in the virus. (Every few years there are also abrupt and radical changes known as antigenic shift, but that's another story). With antigenic drift antibody to last year's virus will recognize this year s virus, but not as well as antibody to this year's virus. That is because white the two viruses still share some epitopes, there are also some epitopes that are different (some old ones go away, and some new ones appear). People at high risk (anybody who has trouble breathing) are immunized every year. Obviously, we want to immunize people against THIS year's virus, but when we immunize them with a vaccine made from this year's virus, most of the antibody response is to the old epitopes still present in this year s virus, and little of the antibody response is to the new epitopes, a phenomenon known as Original Antigenic Sin.' This has obvious important clinical implications. EXPLAIN WHY most of the response is to the old epitopes from last year still present in this year's virus rather than to the new epitopes.Explanation / Answer
Our immune system produces antibodies in response to antigens. There are two types of immune responses observed as primary immune response and secondary immune response.
Now let's see what happens when there is infection of a virus-
When an infection of virus encounter then there is synthesis of antibodies i. e. B and T lymphocytes. This is known as primary response. Sometimes the infection is cleared by this response. During this period, memory plasma cells are also produced. which remember the pathogen and show quick production of antibodies when there is re-infection with the same pathogen. And the process is known as immunological memory. These cells are long lived and whenever there is re-infection of the same virus, there observed a strong response. This is known as secondary immune response. That's why there found a more response to old epitopes of virus that infected last year than this year as memory cells recognizes last year's virus very quickly than this year's virus.
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