Histologic changes in B cell follicles and TZ characteristic of HIV-1 infection. (a) Section of lymph node from an HIV-negative patient. There is one B cell follicle that is normal in size and shape (black arrow). The TZ is normal in size with a normal population of cells (white arrow). (b) Section of a lymph node from an HIV-1–infected patient with presymptomatic HIV-1 infection. The follicles are hyperplastic and disorganized (black arrow), and the TZ is small and somewhat depleted of cells (white arrow). (c) Lymph node section from a patient with AIDS. The follicular space is disorganized and without structure (black arrow), and the TZ is unrecognizable with few cells (white arrow). All images are at a magnification of ×4.