THE SERUM FACTOR FROM PATIENTS WITH ULCERATIVE-COLITIS THAT INDUCES T-CELL PROLIFERATION IN THE MOUSE THYMUS IS INTERLEUKIN-7

The disturbance of immune regulatory T cells is related to the pathoge nesis of ulcerative colitis. Here we demonstrated and characterized th e serum factor from ulcerative colitis patients that induced prolifera tion of intrathymic T cells. The factor isolated from the patient sera by a combination of gel filtration and anion-exchange chromatography induced proliferation of CD4(+)CD8(-) intrathymic T cells in the organ -cultured embryonic mouse thymus, Purification and amino acid sequence analysis of the serum factor demonstrated that the N-terminal 12 sequ ence was homologous to that of interleukin-7, SDS-PAGE and Western blo t confirmed that purified serum factor was interleukin-7. Enzyme immun oassay demonstrated that the serum interleukin-7 concentration was sig nificantly increased in the patients. PCR and Southern blot hybridizat ion demonstrated that interleukin-7 mRNA expression was increased in t he thymus tissues from patients but decreased in the colonic mucosa. S ince interleukin-7 is a crucial cytokine for proliferation and differe ntiation of T cells in the thymus, the present study indicates that in terleukin-7 may contribute to the disturbance of immune regulatory T c ells in ulcerative colitis.