CD4 and HIV-1 infection: For example, the CD4+ T follicular helper (TFH) and T follicular regulatory (TFR) cell subsets within B cell follicles of lymph nodes are more permissive to HIV-1 infection than extrafollicular subsets ex vivo [155,156,157] and comprise a major portion of the latent reservoir during both chronic SIV and HIV infection [158,159,160,161].