IGNOU MCMM 1 2015 - Describe the pathogenesis of AIDS. Explain the mechanisms by which CD4

Question

Describe the pathogenesis of AIDS. Explain the mechanisms by which CD4 + T cells are

destroyed.

24 Jan 2017

Answer :

Word Count : 966

The pathogenesis of AIDS is dependent on the biology of HIV, e.g:

'Trojan horse' mechanism - virus escapes recognition by replication inside monocytes, from where it can spread to other tissues and other hosts.

Latency - Lentiviruses do not show true latency (unlike Herpes viruses or lambda) but do have the capacity to control the expression of their genome by means of virus-encoded trans-acting regulatory proteins (tat and rev).

Antigenic variation - new variants continually arise. In other Lentiviruses such as CAEV, each new antigenic variant results in a flare up of disease. May also occur in HIV and contribute to decline of immune system - 'ratcheting' mechanism due to increasing virus load?

Some of the immune abnormalities in HIV infection include:

Altered cytokine expression

Decreased CTL and NK cell function

Decreased humoral and proliferative response to antigens and mitogens

Decreased MHC-II expression

Decreased monocyte chemotaxis

Depletion of CD4+ cells

Impaired DTH reactions

Lymphopenia

Polyclonal B-cell activation

It is not clear how much of the pathology of AIDS is directly due to the virus and how much is caused by the immune system itself.

The HIV virus is commonly transmitted via unprotected sexual activity, blood transfusions, hypodermic needles, and from mother to child. Upon acquisition of the virus, the virus replicates inside and

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