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HIV that causes AIDS, first starts destroying
A
B-lymphocytes
B
Leucocytes
C
Thrombocytes
D
Helper T-lymphocytes
Detailed Solution
HIV (human immunodeficiency virus) is a retrovirus with an RNA genome.
After entering the body the virus first enters the macrophages, where its RNA is copied into DNA by reverse transcriptase and new viruses are produced; the macrophages act as an HIV factory.
The virus then enters the helper T-lymphocytes ($T_H$ cells, CD4 cells), replicates in them and produces progeny viruses, which attack other helper T-lymphocytes.
This is repeated, leading to a progressive decrease in the number of helper T-lymphocytes in the body.
Helper T cells are needed to activate both B-lymphocytes and other T cells, so their loss cripples the whole immune system and the person becomes prone to opportunistic infections.
So HIV first starts destroying the helper T-lymphocytes.
After entering the body the virus first enters the macrophages, where its RNA is copied into DNA by reverse transcriptase and new viruses are produced; the macrophages act as an HIV factory.
The virus then enters the helper T-lymphocytes ($T_H$ cells, CD4 cells), replicates in them and produces progeny viruses, which attack other helper T-lymphocytes.
This is repeated, leading to a progressive decrease in the number of helper T-lymphocytes in the body.
Helper T cells are needed to activate both B-lymphocytes and other T cells, so their loss cripples the whole immune system and the person becomes prone to opportunistic infections.
So HIV first starts destroying the helper T-lymphocytes.