CD1C and sexually transmitted disease: In order to define the innate and innate-like immune environment within the RM, we first quantified via flow cytometry the following subsets within rectal tissues after collagenase digestion from HIV-negative, sexually transmitted infection (STI)-negative males as a percentage of total CD45 + cells (Fig. 1A–C): neutrophils, macrophages, CD1c + myeloid dendritic cells (mDC), plasmacytoid dendritic cells (pDC), NK, and MZB cells (n = 69), as well as MAIT and γδ T cells (n = 85).