CR1 and infection: Sorted TFH (CD3+CD8-CXCR5hiPD-1hi) were infected with a replication competent X4-tropic HIV GFP reporter virus (X4-HIV) [27] and cultured alone or with FDC (CD45-CD35+), GCB (CD19+CD3-IgD-CD38mid), or both for three days in the presence of saquinavir to prevent spreading infection.