1. Role of CD4+ T-lymphocytes in HIV infection:

• CD4+ T-cells are major target of HIV. This is because T-lymphocytes expresses CD4 molecules as receptor and CXCR4 as co-receptor for viral glycoprotein spike gp120 and gp41.

• CD4+ T –cells are the primary immune cell and is responsible for activation of macrophages for phagocytosis, B-cell for antibody production and secretion of cytokines.

• The results of viral infection causes depletion of CD4 T-cells.

• Most of the infected CD4+ T-cells are destroyed while few survive and revert into resting memory cells, which provide long term latency to HIV.

• Activation of memory T-cell release HIV viruses.

Causes of depletion of CD4+cells in HIV infection:

1. Virus replication
2. Syncytia formation
3. Cytotoxic T-cell lysis of infected CD4+T-cells
4. Antibody dependent cell mediated cytotoxicity (ADCC)
5. Natural killer cell mediated phagocytosis

2. Role of macrophages and monocytes in HIV infection:

• Macrophages and monocytes bearing CD4+ molecules and CCR5 on surface are also targeted by HIV.

• These macrophages and monocytes are the principle cells by which HIV enters to Central Nervous system (CNS) by crossing blood brain barrier (BBB).

• Macrophages and monocytes are affected when the count of CD4+ T- cell deletes rapidly.

• The infected monocytes secretes cytokines in the brain which is responsible for neurological abnormalities in late stage of HIV infection and is one of the AIDS defining condition.

3. Role of lymphoid organ in HIV infection:

• Lymphoid organs play a central role in HIV infection.

• 98% of T-lymphocytes are resides in lymphoid organs

• They serves as reservoir of HIV

Role of CD4+ cells (T-lymphocytes, macrophages and monocytes) and lymphoid organs in HIV infection

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