Two-way correlations between HLA-DRA, HLA-DRB, GAPDH, and B-cell antigens. (A) Plot demonstrating the high degree of correlation of expression between the 2 portions of the HLA heterodimer HLA-DRA and HLA-DRB in DLBCL (0.92, ⋄). This correlation is better than the correlation in the normal control B cells (0.60, ▴). (B) Plot demonstrating the high degree of correlation of expression between 2 different MHC II molecules, HLA-DRA and HLA-DQA, in DLBCL (0.87, ⋄). This correlation is better than the correlation in the normal control B cells (0.60, ▴). (C) Plot demonstrating the lack of correlation of expression between HLA-DRA and the housekeeping gene GAPDH in DLBCL (0.19, ⋄) and normal B cells (0.2, ▴). These results indicate that the coordination of MHC class II genes identified in Figures 3 and 4 is not merely an artifact of microarray loading. (D) Plot demonstrating the lack of correlation between expression of HLA-DRA and the expression of the B-cell antigens CD19 (), CD20 (□), and CD22 (♦) in DLBCL (less than 0.1 for each). These results indicate that variation in MHC class II expression does not result from variable tumor content in specimens, but is a unique property of each patient's disease.