E (Jx1) π (Kx1) J CpGs 1 whole blood sample relative cell type proportions Measurement error 0.78 0.77 0.85 0.82 0.05 0.73 0.81 0.77 0.79 0.02 0.73 0.84 0.83 0.80 0.03 0.78 0.87 0.89 0.83 0.07 ! ! ! ! 0.06 0.09 0.81 0.08 0.07 0.06 0.03 0.77 0.02 0.04 0.08 0.03 Platform-dependent methylation profiles Y ij = πik k=1 K ∑ X jk +εij i = (1,..., N) = whole blood samples j = (1,...., J) = CpGs k = (1,...,K) = cell type profiles