Why would the loss of helper T cells due to HIV infection result in the immunodeficiency associated with AIDS?
A. Helper T cells are central to the activation
of other parts of the immune system.
B. Helper T cells are normally present in
higher numbers, so their loss reduces the
total number of immune cells.
C. Without helper T cells, plasma cells would
not secrete antibody.
D. Infection of the helper T cells could lead to
infection and loss of progenitor cells, thereby
eliminating all immune cells.
A
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The bile salts _____
A) are enzymes B) are manufactured by the pancreas C) emulsify fats in the duodenum D) increase the efficiency of pepsin action E) are normally an ingredient of gastric juice
Which of the following did not play a role in the eradication of smallpox?
A. Ease of diagnosis by readily recognized clinical features B. A short period of infectivity C. No known reservoir outside of human hosts D. The availability of effective antiviral agents that block replication E. All of these characteristics played a role in the eradication of smallpox
The steroid hormone that coordinates molting in arthropods is _____
A) ecdysteroid B) glucagon C) thyroxine D) growth hormone
________ occurs when one living organism feeds on another.
A. Symbiosis B. Mimicry C. Competition D. Predation E. Commensalism