Acquired Immuno Deficiency Syndrome (AIDS) is a medical condition caused by the Human Immunodeficiency Virus (HIV). HIV attacks and weakens the immune system, leading to a reduction in the number of Helper-T cells, which are a type of white blood cell that play a crucial role in coordinating the immune response.

- HIV and its effect on the immune system
HIV primarily targets CD4+ T cells, also known as Helper-T cells, which are a key component of the immune system. These cells are responsible for recognizing foreign substances, activating other immune cells, and coordinating the immune response against infections. HIV infects and replicates within Helper-T cells, leading to their destruction and a subsequent decrease in their population.

- Reduction in number of Helper-T cells
As the HIV infection progresses, the number of Helper-T cells decreases significantly. This reduction weakens the immune system's ability to fight off infections and diseases. Without a sufficient number of Helper-T cells, the immune response becomes compromised, and the body becomes more susceptible to opportunistic infections, which are typically controlled by a healthy immune system.

- Role of Helper-T cells in the immune response
Helper-T cells are essential for initiating and coordinating the immune response. They recognize antigens on pathogens and activate other immune cells, such as B cells and cytotoxic T cells, to mount an effective response against the invading pathogens. They also produce cytokines, which are signaling molecules that regulate the immune system's response to infections.

- Consequences of reduced Helper-T cells
The reduction in Helper-T cells due to HIV infection leads to various consequences:

1. Weakened immune response: With fewer Helper-T cells, the immune system is less capable of mounting an effective defense against infections.

2. Increased susceptibility to infections: The weakened immune system makes individuals more prone to opportunistic infections, such as pneumonia, tuberculosis, and certain types of cancers.

3. Progression to AIDS: When the Helper-T cell count drops below a certain threshold (typically below 200 cells per microliter of blood), the individual is diagnosed with AIDS. At this stage, the immune system is severely compromised, and the risk of developing life-threatening infections and cancers is significantly increased.

In conclusion, Acquired Immuno Deficiency Syndrome (AIDS) is a result of the Human Immunodeficiency Virus (HIV) infection, which leads to a reduction in the number of Helper-T cells. This reduction weakens the immune system and leaves the individual vulnerable to opportunistic infections and diseases.