Increased Expression of Costimulatory Molecules on Peripheral Blood Monocytes in Patients with Crohn's Disease

Abstract

Background: Activation of T lymphocytes and monocytes/macrophages has been implicated in the pathogenesis of Crohn's disease (CD). Costimulatory molecules play important roles in optimal T-cell activation. Methods: With flow cytometric analysis we have investigated the expression of the Costimulatory molecules B7-1 (CD80), B7-2 (CD86), and CD 18 and the intercellular adhesion molecule-1 (ICAM-1) on peripheral blood monocytes and the expression of the activation markers HLA-DR and IL-2R (CD25) on peripheral blood T lymphocytes from 31 CD patients, 17 ulcerative colitis (UC) patients, and 10 healthy controls. Results: In CD patients the percentage of activated T cells (CD3⁺ HLA-DR⁺ and CD3⁺ IL-2R⁺) was significantly increased compared with those of controls and UC patients (P < 0.05). Most monocytes from all three groups expressed B7-2, CD18, and ICAM-1 molecules (all >79%), but only a few positive cells expressed B7-1 molecules (< 5%). No significant differences were detected in the percentage positivity of all Costimulatory molecules tested among CD, UC, and controls. The mean fluorescence intensity (MFI) of B7-1 in all three groups was very weak and not significantly different. However, in CD patients there was a significantly increased MFI of B7-2, CD 18, and ICAM-1 molecules compared with UC and controls (P < 0.05). On the other hand, both the percentage positivity and MFI of HLA-DR molecules on monocytes of UC patients were significantly lower than those of CD patients and controls (P < 0.05). Conclusions: Expression of the Costimulatory molecules B7-2, CD 18, and ICAM-1 on peripheral blood monocytes of CD patients is increased. In CD patients activation of peripheral T lymphocytes may correlate with increased expression of these Costimulatory molecules on peripheral blood monocytes.

Key Words:

• Costimulatory molecule
• Crohn's disease
• flow cytometry
• HLA-DR
• monocyte
• ulcerative colitis