All infiltrating T‐lymphocytes in Hodgkin's disease express immunohistochemically detectable T‐cell receptor ζ‐chains in situ

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Abstract
Aim: We studied the expression of TCR ζ‐chain on tumour‐infiltrating lymphocytes in EBV‐positive and EBV‐negative cases of Hodgkin's disease (HD), to assess whether downregulation of TCR ζ‐chain on tumour‐infiltrating lymphocytes might be a mechanism for immune escape of the neoplastic cells.Methods and results: By immunohistochemistry we investigated tissue of 27 cases of primary HD, both paraffin embedded and frozen, for the presence of T‐cell receptor complex ζ‐chain and other T‐cell markers on the reactive cells. Strong membranous staining of TCR ζ‐chain was present in all cases in frozen tissue. In contrast, in paraffin‐embedded material substantial loss of TCR ζ‐chain was detected in old (> 6 years) tissues. However, no differences in either the number of positive cells or their staining intensity were observed in EBV‐positive and negative cases of HD as detected in frozen tissue. Storage of paraffin‐embedded tissue leads to a rapid and substantial loss of TCR ζ‐chain reactivity compared to frozen material of the same HD cases. Staining reactivity of other T‐cell markers (CD3, CD4 and CD8) on paraffin‐embedded material remained unaffected. Immunofluorescent double‐staining confirmed colocalization and coexpression of TCR ζ‐chain and CD3.Conclusions: In frozen biopsies of primary HD TCR ζ‐chain was expressed on all reactive CD3‐positive cells, both in EBV‐positive and EBV‐negative cases. This suggests that ζ‐chain downregulation is not a likely mechanism whereby neoplastic cells of HD can escape immune surveillance.