The common lymphoid progenitor (CLP) gives rise to all lymphocyte lineages, including B cells (not pictured) and T cells. In the T cell lineage, the CLP gives rise to the double positive (CD4+CD8+, DP) stage in the thymus. This DP cell can give rise to conventional CD4, CD8 or innate-like T cells. The CLP also gives rise to NK cells through an NK-committed progenitor (NKP), to lymphoid tissue inducer cells (LTi), and to helper ILC lineages through the common helper innate lymphoid progenitor (CHILP). There also exist tissue-resident innate lymphocytes with cytotoxic potential, although their lineage remains unclear. Cells with this phenotype may arise from the NK lineage, which would categorize them as tissue-resident NK cells (TR-NK), from the CHILP, which would categorize them as killer ILC1 (ILC1k), or they may have a distinct progenitor. Marker expression patterns of various type 1 innate lymphocyte subsets are listed.