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

Aim: We studied the expression of TCR zeta-chain on tumour-infiltrating lym phocytes in EBV-positive and EBV-negative cases of Hodgkin's disease (HD), to assess whether downregulation of TCR zeta-chain on tumour-infiltrating l ymphocytes might be a mechanism for immune escape of the neoplastic cells. Methods and results: By immunohistochemistry we investigated tissue of 27 c ases of primary HD, both paraffin embedded and frozen, for the presence of T-cell receptor complex zeta-chain and other T-cell markers on the reactive cells. Strong membranous staining of TCR zeta-chain was present in all cas es in frozen tissue. In contrast, in paraffin-embedded material substantial loss of TCR zeta-chain was detected in old (> 6 years) tissues. However, n o differences in either the number of positive cells or their staining inte nsity 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 su bstantial loss of TCR zeta-chain reactivity compared to frozen material of the same HD cases. Staining reactivity of other T-cell markers (CD3, CD4 an d CD8) on paraffin-embedded material remained unaffected. Immunofluorescent double-staining confirmed colocalization and coexpression of TCR zeta-chai n and CD3. Conclusions: In frozen biopsies of primary HD TCR zeta-chain was expressed on all reactive CD3-positive cells, both in EBV-positive and EBV-negative c ases. This suggests that zeta-chain downregulation is not a likely mechanis m whereby neoplastic cells of HD can escape immune surveillance.