Describe how the lymphocyte development in the thymus minimizes T cells capable of
inducing autoimmunity while maintaining T cells capable of recognizing foreign
antigens.
What will be an ideal response
Immature T cells in the thymus undergo two selection processes—positive and negative. First, in order to react to
foreign antigen, T cells must be able to bind to the foreign antigen presented in conjunction with MHC antigens on
antigen presenting cells. In positive selection, only T cells capable of binding to MHC can bind to MHC in the
thymus live. Cells without the capability of binding to MHC do not bind to the appropriate cells and die by
apoptosis. Second, T cells that have receptors for self-antigens must not be allowed to live. T cells that react to
self-antigens in the thymus in conjunction with MHC are eliminated. Thus, the only T cells remaining should react
with MHC and any non-self antigens presented with it.
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Answer the following statement true (T) or false (F)
All of the following are standards used for diagnosing anorexia nervosa EXCEPT
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Which principle described by psychologist Martin Seligman fosters an overall positive attitude by using thinking and behavior techniques to resist negativity?
A) Learned helpfulness B) Learned pessimism C) Learned optimism D) Learned mindfulness
Which of the following portions of the spine have a convex curve anteriorly?
A. Thoracic and sacrococcygeal B. Cervical and lumbar C. Cervical and thoracic D. Lumbar and sacrococcygeal