Immune cell subsets and expression of immunoregulatory molecules in EBV⁺compared with EBV⁻CHL specimens. Markers were detected by IHC and quantified as detailed in “Methods.” Diamond symbols indicate average values for triplicate scores for an individual tumor specimen (see “Methods”). Bars indicate mean values and standard error of the mean. P values from the Wilcoxon rank sum test were >.1 unless indicated.