Peripheral and intestinal lymphocyte activation after in vitro exposure to cow's milk antigens in normal subjects and in patients with Crohn's disease

We studied in Crohn's disease and controls the in vitro activation of either peripheral (PBMNC) or intestinal (LPMNC) mononuclear cells in response to the cow's milk antigen β-lactoglobulin (Blg). The activation of mononuclear cells was investigated by analyzing the kinetics of the transferrin receptor (T9 antigen) and interleukin 2 receptor (Tac antigen) expression. In both controls and Crohn's disease patients Blg (1 μg/ml) induced a significant ( P < 0.01) increase of T9 and Tac expression by both PBMNC and LPMNC cultured for 3 days. After Blg exposure the counts of T9- and Tac-bearing cells were significantly ( P < 0.05) higher in PBMNC cultures from healthy controls than in those from patients with Crohn's disease. In both groups peripheral T-enriched cell suspensions did not express T9 and Tac when stimulated with Blg but were restored to express either antigen by the addition of 10% autologous adherent cells. In LPMNC cultures from patients with Crohn's disease the Tac expression after 3 days of Blg stimulation was significantly ( P < 0.05) higher than in the autologous PBMNC. Data from this study indicate that in both controls and patients with Crohn's disease lymphocytes sensitized to Blg occur in the circulation as well as in the gut lamina propria. Our data also suggest that in Crohn's disease an increased proportion of lymphocytes sensitized to Blg are recruited from the circulation into the site of the intestinal lesion.