MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I MOLECULE EXPRESSION IS NORMAL ON PERIPHERAL-BLOOD LYMPHOCYTES FROM PATIENTS WITH INSULIN-DEPENDENTDIABETES-MELLITUS

Recent work from one laboratory has shown, in both non-obese diabetic mice and humans, an association between insulin-dependent diabetes mel litus (IDDM) and quantitative difference in MHC class I molecule expre ssion. This reported decrease in MHC class I molecule expression is ve ry controversial in the nonobese diabetic mouse model of IDDM, but to our knowledge, it has not been evaluated by another group in human IDD M. To evaluate this question, we studied 30 patients with IDDM and 30 age- and sex-matched normal controls. MHC class I molecule expression was measured by flow cytometry with conformational-dependent MHC class I mAbs. The mean antigen density of MHC class I molecule expression i n IDDM vs. normal control is 454+/-34 vs. 440+/-28 for lymphocytes and 1,440+/-117 vs. 1,494+/-117 for monocytes, both P >0.05. Three confor mational-dependent MHC class I antibodies showed consistent results. T o estimate the biological variation of MHC class I molecule expression in normal controls, we also studied 10 age- and sex-matched normal co ntrol pairs. Using (X) over bar+/-SD of the percentage difference of m ean antigen density in the normal control pairs as our definition of n ormal, we found that 70% (21/30) of IDDM patients had normal, 13% (4/3 0) of IDDM patients had decreased, and 17% (5/30) of IDDM patients had increased MHC class I molecule expression on lymphocytes. All IDDM pa tients showed normal MHC class I expression on monocytes. In conclusio n, we find that there is no consistent decrease in MHC class I molecul e expression on either lymphocytes or monocytes from patients with IDD M. The MHC class I molecule expression observed in IDDM patients is la rgely within the expected biological variation of MHC class I molecule expression that has been observed in normal controls.