Intestinal Lin(-)c-Kit(+)NKp46(-)CD4(-) Population Strongly Produces IL-22 upon IL-1 beta Stimulation

Abstract

Small intestinal innate lymphoid cells (ILCs) regulate intestinal epithelial cell homeostasis and help to prevent pathogenic bacterial infections by producing IL-22. In a global gene-expression analysis comparing small intestinal ILCs (Lin(-)c-Kit(+)Sca-1(-) cells) with non-ILCs (Lin(-)c-Kit(-)Sca-1(-) cells), we found that Lin(-)c-Kit(+)Sca-1(-) cells highly expressed the mRNAs for Il22, antimicrobial peptides, Csf2rb2 (Il3r), mast cell proteases, and Rorc. We then subdivided the Lin(-)c-Kit(+)Sca-1(-) cells into three groups-Lin(-)c-Kit(+)NKp46(-)CD4(-), Lin(-)c-Kit(+)NKp46(-)CD4(+) (CD4(+) LTi-like cells), and Lin(-)c-Kit(+)NKp46(+) (NKp46(+) ILC22 cells)-and showed that the Lin(-)c-Kit(+)NKp46(-)CD4(-) cells produced the highest level of IL-22 protein after IL-1 beta, IL-23, or IL-1 beta and IL-23 stimulation. In addition, we showed that the majority of the Lin(-)c-Kit(+)NKp46(-)CD4(-) population was IL-7R alpha(+)CD34(-)beta 7(int) cells, and IL-7R alpha(-) cells could be divided into three subsets (CD34(+)beta 7(int), CD34(-)beta 7(int), and CD34(int)beta 7(hi) cells). The IL-7R alpha(+)CD34(-)beta 7(int) cells strongly expressed the transcripts for Il17f and Il22 after costimulation with IL-1 beta and IL-23. The IL-7R alpha(-)CD34(+)beta 7(int) and IL-7R alpha(-)CD34(int)beta 7(hi) cells predominantly expressed the transcripts for mast cell proteases and differentiated almost entirely into mast cells after 1 wk in culture medium supplemented with a cytokine mixture, whereas the IL-7R alpha(-)CD34(+)beta 7(int) cells highly expressed alpha-defensins and showed no differentiation. Taken together, these findings indicate that the IL-7R alpha(-)CD34(+)beta 7(int) and IL-7R alpha(-)CD34(int)beta 7(hi) populations are mast cell progenitors, and the IL-7R alpha(-)CD34(-)beta 7(int) (CD4(-) LTi-like cells) and IL-7R alpha(-)CD34(-)beta 7(int) populations within Lin(-)c-Kit(+)NKp46(-)CD4(-) cells may control intestinal homeostasis and provide intestinal protection by producing high levels of IL-22 and alpha-defensins, respectively.