Researchers debate the evolutionary value to the virus of its ability to cause disease. Many argue that viruses accidentally cause disease and only in animals that are not the natural host. They state that this strategy may eventually prove fatal to the virus’s future in that host. It is reasoned that the animals will eventually develop immune mechanisms to combat the virus and prevent its spread. Another group of researchers supports the view that disease is a way to enhance the survival of the virus. What position would you take, and what arguments would you give to support your view?
Why should B cells residing in the mucosa-associated lymphoid tissues produce IgA?
Many dairy operations keep cow’s milk for sale and use formula and feed to raise any calves. One farmer noticed that calves raised on the formula and feed needed to be treated for diarrhea more frequently than calves left with their mothers to nurse. He had some tests run on the diets and discovered no differences in the calories or nutritional content. The farmer called a veterinarian and asked him to explain the observations. What was the vet’s response?
What kinds of diseases would be expected to occur as a result of lack of T or B lymphocytes?
How is graft-versus-host disease difference from a recipient’s rejection of donor tissue?
Define allergen, and give five common examples of substances that act as allergens.
How could you determine whether an immunodeficiency disease affects T lymphocytes, B lymphocytes, or macrophages?
An ELISA test is used to screen patient specimens for HIV. A positive ELISA test is confirmed by a Western blot test. Why not the other way around, with the ELISA second?
The rate of nosocomial infections is often relatively high in emergency room settings. Explain why this might be so.
A filter capable of preventing bacteria from passing is placed at the bottom of a U tube to separate the two sides. Streptomycin-resistant cells of a bacterial strain are placed on one side of the filter and streptomycin-sensitive cells are placed on the other side. After incubation, the side of the tube that originally contained only streptomycin-sensitive cells now contains some streptomycin-resistant cells. Give three possible reasons for this observation. What further experiments would you do to determine the correct explanation? Three possible reasons: 1. The streptomycin sensitive cells mutated to resistance. 2. The streptomycin sensitive cells were transformed to streptomycin resistance by DNA- mediated transformation 3. The streptomycin sensitive cells were transduced to streptomycin resistance by transduction