Question

How does HIV confound the human immune system?

Short answer

HIV targets and destroys CD4 cells, weakening the immune system's defense capabilities.

Step-by-step solution

Understand HIV and the Immune System

HIV stands for Human Immunodeficiency Virus. It attacks the body's immune system, specifically the CD4 cells (T cells), which are crucial for immune defense.

Mechanism of HIV Entry

HIV enters the human body and targets CD4 cells by binding to receptors on the cell surface. Once inside, the virus releases its RNA into the host cell.

Replication of HIV

Inside the CD4 cell, HIV uses an enzyme called reverse transcriptase to convert its RNA into DNA. This new DNA is then integrated into the host cell’s DNA by another enzyme called integrase.

Production of New Virus Particles

The infected cell begins to produce new HIV particles, which are released into the bloodstream to infect other CD4 cells, reducing the body's immune capability.

Destruction of CD4 Cells

Over time, HIV destroys more and more CD4 cells, weakening the immune system and making the body more susceptible to infections and diseases.

Key concepts

CD4 cells

CD4 cells, also known as T-helper cells, are a type of white blood cell that plays a vital role in the immune system. These cells are essential for the body's defense mechanism because they signal other immune cells to perform their functions. When HIV infects CD4 cells, it significantly hampers the immune system's ability to tackle infections. The virus targets these cells by attaching itself to certain receptors on their surface, making the body less capable of defending against various diseases.

reverse transcriptase

Reverse transcriptase is a special enzyme used by HIV to replicate itself inside human cells. After the virus enters a CD4 cell, it releases its genetic material in the form of RNA. Reverse transcriptase then converts this RNA into DNA, a process that is unique because it works in reverse compared to typical cell processes that convert DNA to RNA. This newly created viral DNA is then inserted into the host cell's DNA, allowing the virus to hijack the cell's machinery to produce more HIV particles.

integrase

Integrase is another critical enzyme for HIV replication. After reverse transcriptase converts the virus's RNA into DNA, integrase takes this viral DNA and integrates it into the host cell's own DNA. By doing this, the viral DNA becomes a permanent part of the CD4 cell's genetic material. This step is crucial because it essentially transforms the infected cell into a factory for producing more HIV. Every time the CD4 cell divides, it also replicates the integrated viral DNA, spreading the infection further.

immune system suppression

HIV causes immune system suppression by consistently targeting and destroying CD4 cells. As the number of CD4 cells declines, the body's ability to fend off infections diminishes. This suppression makes individuals with HIV more susceptible to opportunistic infections and certain cancers, which a healthy immune system would normally control. Over time, if untreated, this weakening of the immune system leads to AIDS (Acquired Immunodeficiency Syndrome), the most severe phase of HIV infection.

HIV replication

HIV replication is a complex process involving several steps. Once inside a human body, the virus binds to CD4 cells and releases its RNA. Using reverse transcriptase, the RNA is converted into DNA, which is then integrated into the host cell's DNA by the enzyme integrase. The infected CD4 cell uses its machinery to produce new viral particles. These particles are then assembled and released to infect more CD4 cells. This cycle continues, leading to a gradual decline in the number of functional CD4 cells and weakening the immune system over time.