Promoter H3K4 methylation dynamically reinforces activation-induced pathways in human CD4 T cells.

The epigenetic determinants driving the responses of CD4 T cells to antigen are currently an area of active research. Much has been done to characterize helper T-cell subsets and their associated genome-wide epigenetic patterns. In contrast, little is known about the dynamics of histone modifications during CD4 T-cell activation and the differential kinetics of these epigenetic marks between naive and memory T cells. In this study, we have detailed the dynamics of genome-wide promoter H3K4me2 and H3K4me3 over a time course during activation of human naive and memory CD4 T cells. Our results demonstrate that changes to H3K4 methylation occur relatively late after activation (5 days) and reinforce activation-induced upregulation of gene expression, affecting multiple pathways important to T-cell activation, differentiation and function. The dynamics and mapped pathways of H3K4 methylation are distinctly different in memory cells, which have substantially more promoters marked by H3K4me3 alone, reinforcing their more differentiated state. Our study provides the first data examining genome-wide histone modification dynamics during CD4 T-cell activation, providing insight into the cross talk between H3K4 methylation and gene expression, and underscoring the impact of these marks upon key pathways integral to CD4 T-cell activation and function.

Protection against colitis by CD100-dependent modulation of intraepithelial γδ T lymphocyte function.

Intraepithelial γδ T lymphocytes (γδ IEL) have important roles in repair of tissue damage at epithelial sites, such as skin and intestine. Molecules that orchestrate these γδ T-cell functions are not well defined. Recently, interaction of the semaphorin CD100 on skin γδ T cells with plexin B2 on keratinocytes was shown to be important for effective γδ T-cell function in the epidermis, which raised the possibility that CD100 may exert similar functions in the intestinal tract. In this study, we find that CD100 is expressed on all IEL, and plexin B2 is present on all epithelial cells of the mouse colon. Using the dextran sulfate sodium (DSS) mouse model of colitis, disease severity is significantly exacerbated in CD100-deficient (CD100(-/-)) mice, with increased colon ulceration and mucosal infiltration with inflammatory cells. The severe colitis in CD100(-/-) mice is attributable to the failure of the colon epithelium to mount a proliferative response to damage. Unlike wild-type γδ IEL, γδ IEL from CD100(-/-) mice fail to produce keratinocyte growth factor-1 (KGF-1) in response to DSS treatment. Administration of recombinant KGF-1 to CD100(-/-) animals ameliorates disease and reverses colitis susceptibility. These results demonstrate that CD100-mediated signals are critical for effective activation of γδ IEL to produce growth factors, including KGF-1, that are required for healing of the colon epithelium during colitis.