HIV infects cells in the central nervous system and the immune system. HIV's main target cell is the T helper lymphocyte. These cells play a crucial role in the immune system, by coordinating the actions of other immune system cells.A large reduction in the number of T helper cells seriously weakens the immune system.he 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.