Flow cytometry gating procedures. Representative dot plot examples of (A) side scatter (SSC) versus CD3, (B) SSC versus CD4, and (C) SSC versus CD8 used for identification of T cells, T-helper cells, and T cytotoxic cells, respectively. Specimens were prepared by whole blood lysis as detailed in Materials and Methods. The individual gating regions (R1, R2, and R3) denote the live gates used for data acquisition.