Question

AIDS is caused by HIV, which principally infects

• A. All lymphocytes
• B. Activator B cells
• C. T-4 lymphocytes
• D. Cytotoxic T cells

Answer 1

Answer: (C)

T-4 lymphocytes

HIV infects vital cells in the human immune system such as helper T cells (specifically $C{D}_4^{+}$ T cells or T-4 lymphocytes), macrophages and dendritic cells. HIV infection leads to low levels of $C{D}_4^{+}$ T cells through a number of mechanisms, including pyroptosis of abortively infected T cells, apoptosis of uninfected bystander cells, direct viral killing of infected cells and killing of infected $C{D}_4^{+}$ T cells by $C{D}_8$ cytotoxic lymphocytes that recognize infected cells. When $C{D}_4^{+}$ T cell numbers decline below a critical level, cell-mediated immunity is lost and the body becomes progressively more susceptible to opportunistic infections.