After infection, the CD4 count measured in blood generally reduces in the first month or two and then recovers, but not to the pre-infection level.
Then, usually over many years the CD4 count reduces until HIV advances to cause symptoms.
Anti-retroviral treatment stops the decline in CD4 cells which then usually recover and get stronger again.
With HIV there is a lot of individual variability in how fast this takes. Some people need treatment soon after infection and other can still have a strong CD4 count after 15 years without treatment.
helper T cells
The role of the CD4 receptors in HIV is so that the virus fuses with the T helper cells.
HIV can only bind with the CD4 located on Helper T cells.
T helper cells, also called CD4+ T cells (or just CD4 cells) are part of the immune system, but they are also the main target cells that HIV infects and uses to reproduce.
Infected CD4 T-cells
HIV attacks and kills CD4 helper T cells.
HIV infects only the CD4 cells of the immune system, and it destroys lymphocytes.
The Human Immunodeficiency Virus (HIV) seems to only infect the CD4 (or T-helper) cells of the immune system. The CD4 cells are responsible for activating and directing other immune system cells. HIV also infects macrophages and microglial cells that express the CD4 molecule on their surface. The virus can also infect a subtype of myeloid dendritic cells MDC-1.
Once the HIV virus enters the body, it seeks out specific white blood cells called CD4 T-helper cells. It than begins the process of entry and replication using the mechanism of the CD4 cells. This allows the virus to multiply and grow. In time, the HIV virus will overtake and destroy all CD4 cells which the body needs as a defense against illness. The destruction of CD4 cells makes the body vulnerable to opportunistic infections, thereby causing illness in those infected.
An abnormally low number of CD4+ T lymphocytes is an indication of AIDS, the disease caused by HIV. Without enough CD4+ T cells, you are much more vulnerable to infection.
That is unlikely, since the HIV virus directly attacks the CD4 cells. In time, the virus will destroy all CD4 cells. Without medications, that will happen sooner rather than later.
Nope, T helper cells are HIV's target cells.