Comparison of relative cell and mRNA proportions. Relative cell proportions determined by immunohistochemistry (open circles; Table 5), relative mRNA proportions calculated by Robust Computational Reconstitution (solid squares; Table 1, MAS-S t), and relative mRNA proportions according to model equation (1) (solid triangles; fit to the computed relative mRNA proportions). The square root of the coefficient of determination is R = 0.90. The regression p-value is p = 10-6 (least squares regression of 18 values using 2 parameters). The fitted model mRNA proportions are similar to the cell proportions multiplied by a constant factor reflecting the respective cellular mRNA content. Part of the large apparent differences in cellular mRNA content can possibly be attributed to differential mRNA yield due to experimental methodology, like mRNA extraction and amplification, or differential specificities of the cell type markers used in immunohistochemistry.