CCL4 and HIV infectious disease: To ensure that the rate of HIV infection of CD57+ memory CD4+ T cells did not interfere with the interpretation of the effect of MIP-1β production on HIV infection, we also sorted CMV-specific memory CD4+ T cells (cells that were CD45RO+ or CD45RO−CD27−) into populations which did or did not respond to CMV pp65 peptides based on IFNγ production after a six hour incubation.