Cytotoxic T cells (T lymphocytes, CTL) function to kill HIV and HIV infected cells.
Secondary lymphoid organs, such as the spleen and lymph nodes, are the sites where most HIV replication is concentrated.
B cell follicles are a part of secondary lymphoid organs such as the spleen and lymph nodes. HIV is adept at hiding in B cell follicles, allowing it to escape immune surveillance from CTL, and causing persistent infection.