INCREASED INVITRO RELEASE OF SOLUBLE INTERLEUKIN-2 RECEPTOR BY COLONIC LAMINA PROPRIA MONONUCLEAR-CELLS IN INFLAMMATORY BOWEL-DISEASE

Increased concentrations of the soluble form of the interleukin 2 receptor have been observed in the sera of Crohn's disease and ulcerative colitis patients. In this study we have observed the spontaneous release of soluble interleukin 2 receptor by unstimulated, isolated normal and inflammatory bowel disease colonic lamina propria mononuclear cells. Lamina propria mononuclear cells from Crohn's disease patients (median = 204 U/ml (interquartile range 126-396, n 17) secreted significantly (p < 0.01) more soluble interleukin 2 receptor than normal controls (median = 124.5 U/ml (108-131), n 12). No statistically significant differences were seen between ulcerative colitis (median = 135 U/ml (92-196), n 20) and normal controls. Moreover, significantly (p < 0.01) increased amounts of soluble interleukin 2 receptor were secreted by colonic diverticulitis lamina propria mononuclear cells (median = 259 U/ml (149-282), n 15) which were used as disease specificity controls. Time course experiments showed that the majority of soluble interleukin 2 receptor was released by isolated lamina propria mononuclear cells in the first six days of culture. Upon stimulation with pokeweed mitogen, Crohn's disease (median = 2258 U/ml (1435-3584), n 14), normal control (median = 2622 U/ml (2030-3180), n 14) and diverticulitis lamina propria mononuclear cells (median = 2745 U/ml (1733-3192), n 10) reached similar maximal soluble interleukin 2 receptor secretion levels, while ulcerative colitis lamina propria mononuclear cells secreted significantly (p < 0.005) less soluble interleukin 2 receptor (median = 912 U/ml (494-1259), n 17). These results suggest that enhanced shedding/secretion of soluble interleukin 2 receptor by intestinal lymphocytes may account in part for increased serum soluble interleukin 2 receptor concentrations during chronic intestinal inflammatory reactions.