C3.2.12 Infection of lymphocytes by HIV with AIDS as a consequence Notes

How HIV Infects Lymphocytes

1. HIV targets helper T-cells, a type of lymphocyte critical for coordinating immune responses.
2. The virus binds to the CD4 receptor on the surface of these cells, allowing it to enter.
3. Inside the cell, HIV uses an enzyme called reverse transcriptase to convert its RNA into DNA.
4. This viral DNA integrates into the host cell’s genome, turning the cell into a factory for producing new viruses. viral DNA integrates into the host cell’s genome, turning the cell into a factory for producing new viruses.

The Role of Helper T-Cells in Immunity

1. Helper T-cells are essential for activating other immune cells, such as:
   1. B-lymphocytes: These cells produce antibodies that neutralize pathogens.
   2. Cytotoxic T-cells: These cells destroy infected or cancerous cells.
2. Without helper T-cells, the immune system cannot effectively coordinate these responses.

The Progression from HIV to AIDS

1. Initial Infection: After exposure, HIV rapidly multiplies, causing flu-like symptoms. During this stage, the immune system produces antibodies against the virus.
2. Latency Period: The virus remains active but hidden, gradually destroying helper T-cells. This phase can last for years without noticeable symptoms.
3. AIDS: When the number of helper T-cells (Also called CD4 cells) falls below a critical level, the immune system becomes severely compromised. This stage is characterized by:
   1. Opportunistic Infections: Diseases like tuberculosis, pneumonia, and certain cancers that a healthy immune system would typically control.
   2. Marker Diseases: Conditions like Kaposi’s sarcoma, a rare cancer, which are often used to diagnose AIDS.
4. Final stage: AIDS (Acquired Immunodeficiency Syndrome) is diagnosed when the helper T-cell count drops below 200 cells/mm³ (normal range: 500–1,500 cells/mm³) or when the patient develops severe opportunistic infections or cancers.