To determine which immune cell types are recruited, we isolated human CD14+ monocytes, CD3+ T cells, and CD19+ B cells, labeled each population with a different fluorescent cell tracker, mix them at a ratio of 6:3:1 (monocytes: T cells: B cells), and perfused the mixture through the vascular channel of the chip 24 h after infection (Supplementary Fig. 6f). This evidence concerns the gene CD19 and infection.