Why is a person with AIDS susceptible to infections diseases?

People with AIDS are susceptible to infections diseases due to a severely weakened immune system. AIDS (acquired immunodeficiency syndrome) is the most advanced stage of HIV (human immunodeficiency virus) infection. HIV primarily targets and destroys a type of white blood cell called CD4+ T cells, also known as helper T cells, which play a crucial role in the body's immune defense. As the number of CD4+ T cells decreases, the immune system becomes progressively weaker and less effective in fighting off infections.

Here's how a weakened immune system in individuals with AIDS increases their susceptibility to infections diseases:

1. Opportunistic Infections: AIDS compromises the body's ability to defend itself against infections caused by opportunistic pathogens. These pathogens are organisms that typically do not cause illness in individuals with healthy immune systems. However, they can take advantage of the weakened defenses in people with AIDS and cause severe infections. Examples of opportunistic infections commonly seen in AIDS patients include:

- Pneumocystis jirovecii pneumonia (PCP)

- Cryptosporidium and microsporidia

- Toxoplasmosis

- Cryptococcus

- Cytomegalovirus (CMV)

- Kaposi's sarcoma

2. Reduced Antibody Production: CD4+ T cells are essential for helping B cells produce antibodies. Antibodies are proteins that recognize and bind to specific antigens, marking them for destruction by other immune cells. With a reduced number of CD4+ T cells, the production of antibodies is impaired, leading to a weakened ability to fight off infections.

3. Impaired Cellular Immunity: CD4+ T cells are crucial in coordinating cellular immune responses. They activate other immune cells, such as CD8+ T cells (also known as cytotoxic T cells) and macrophages, which directly destroy infected cells and pathogens. The lack of functional CD4+ T cells disrupts this process, making it more difficult to clear infections.

4. Increased Viral Replication: HIV itself continues to replicate and damage immune cells, further weakening the immune system. The ongoing viral replication also increases the likelihood of mutations that can lead to drug resistance, complicating treatment efforts.

In summary, a weakened immune system due to HIV infection and the loss of CD4+ T cells in people with AIDS make them highly susceptible to various opportunistic infections and other diseases that would normally be controlled by a healthy immune response.