What disease suppresses the immune system?

The most common disease that suppresses the immune system is HIV (Human Immunodeficiency Virus) infection, which leads to Acquired Immunodeficiency Syndrome (AIDS). HIV primarily targets and destroys a type of white blood cell known as CD4+ T cells or "helper T cells," which play a crucial role in coordinating the immune response against infections. As a result, people with HIV have a weakened immune system and are more susceptible to various opportunistic infections and cancers, leading to life-threatening illnesses.

Here's a brief explanation of how HIV affects the immune system:

1. HIV Entry and Infection: The HIV virus enters the body through contact with infected blood, semen, vaginal fluids, or breast milk. Once inside the body, it primarily infects CD4+ T cells.

2. CD4+ T Cell Depletion: HIV hijacks the cellular machinery of CD4+ T cells to make copies of itself and produce new viral particles. As the number of infected T cells increases, the overall count of healthy CD4+ T cells decreases, weakening the immune system's ability to fight infections.

3. Impaired Immune Response: With reduced levels of CD4+ T cells, the immune system's ability to detect and respond to foreign pathogens is compromised. This leads to an increased susceptibility to opportunistic infections and certain types of cancers.

4. Opportunistic Infections: People with HIV often develop infections caused by microorganisms that don't usually cause illness in individuals with healthy immune systems. Common opportunistic infections associated with HIV include Pneumocystis jirovecii pneumonia (PCP), toxoplasmosis, cryptococcal meningitis, and Kaposi's sarcoma (a type of cancer caused by a virus).

5. CD8+ T Cell Function and Memory B Cells: While HIV primarily targets CD4+ T cells, it can also affect CD8+ T cells (cytotoxic T cells) and memory B cells, further weakening the body's defenses.

It's important to note that effective antiretroviral therapy (ART) can significantly slow down the progression of HIV infection and preserve the immune system. With regular adherence to ART, people with HIV can live long, healthy lives by maintaining a low viral load and preventing the onset of opportunistic infections and AIDS-related complications.