MCQ
$HIV$ that causes $AIDS$, first starts destroying
- ✓helper Tlymphocytes
- Bthrombocytes
- C$B$-lymphocytes
- Dleucocytes.
✓
Answer
Correct option: A.
helper Tlymphocytes
a
(a) : The $AIDS$ retrovirus, called human immunodeficiency virus $(HIV)$, mounts a direct attack on $CD4^+\ T$ helper cells because it recognizes the $CD4$ coreceptors associated with these cells. $HIV’s$ attack on $CD4^+\ T$ cells cripples the immune system in at least three ways. First, HIVinfected cells die only after releasing replicated viruses that infect other $CD4^+\ T$ cells, until the entire population of $CD4^+\ T$ cell is destroyed. Second, $HIV$ causes infected $CD4^+ \ T$ cells, to secrete a soluble suppressing factor that blocks other $T$ cells from responding to the $HIV$ antigen. Finally, $HIV$ may block transcription of $MHC$ genes, hindering the recognition and destruction of infected $CD4^+\ T$ cells, and thus protecting those cells from any remaining vestiges of the immune system. The combined effect of these responses to $HIV$ infection is to wipe out the human immune defense.
(a) : The $AIDS$ retrovirus, called human immunodeficiency virus $(HIV)$, mounts a direct attack on $CD4^+\ T$ helper cells because it recognizes the $CD4$ coreceptors associated with these cells. $HIV’s$ attack on $CD4^+\ T$ cells cripples the immune system in at least three ways. First, HIVinfected cells die only after releasing replicated viruses that infect other $CD4^+\ T$ cells, until the entire population of $CD4^+\ T$ cell is destroyed. Second, $HIV$ causes infected $CD4^+ \ T$ cells, to secrete a soluble suppressing factor that blocks other $T$ cells from responding to the $HIV$ antigen. Finally, $HIV$ may block transcription of $MHC$ genes, hindering the recognition and destruction of infected $CD4^+\ T$ cells, and thus protecting those cells from any remaining vestiges of the immune system. The combined effect of these responses to $HIV$ infection is to wipe out the human immune defense.
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