Mycobacterium tuberculosis and Listeria monocytogenes are both facultative intra
ID: 178244 • Letter: M
Question
Mycobacterium tuberculosis and Listeria monocytogenes are both facultative intracellular parasites in humans. These pathogens have the ability to grow and multiply inside phagocytes. Artificial passive immunity against these infections can be achieved only by transferring E rosette forming leukocytes along with their corresponding adherent cells from an immune individual. E-rosette forming cells alone are incapable of effecting this transfer. Transferring E rosette forming leukocytes along with their corresponding adherent cells from a tuberculin skin positive individual will confer passive immunity to an individual undergoing a mixed lung infection caused by Mycobacterium tuberculosis and Listeria monocytogenes. However, such transfer will not confer immunity to an individual who is infected only with Listeria monocytogenes.
In full detail, explain the nature of this immunologic discrepancy.
Explanation / Answer
A tuberculin skin test detects if an individual has ever been exposed to tuberculosis antigens. If the result of this test is positive, the individual is said to be a tuberculin skin positive individual. Such an individual has developed several E Rosette lymphocytes as an immune response because of exposure to TB antigens. These E Rosette lymphocytes comprise a central T lymphocyte cell specific to the TB antigen, surrounded by a number of red blood cells in a circular or rosette-like manner. These E rosettes can kill TB antigens. Hence, when these E rosettes are transferred to a person suffering from mixed lung infection caused by M.tuberculosis as well as L.Monocytogenes, they will identity the M.Tuberculosis antigens housed within phagocytes and attack them. Since listeria monocytogenes also live in phagocytes, they also get destroyed. However, these E rosettes will not be helpful to treat a person with only L.monocytogenes as the E rosettes are specific to TB antigens.
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