CD69 expression correlates with expression of other markers of Th1 T cell differentiation in peripheral T cell lymphomas.

CD69, a marker of early T cell activation, is associated with Th1 T cell differentiation. Previously we found that peripheral T cell lymphomas could be subdivided based on the expression of markers of Th1 versus Th2 differentiation, including CXCR3, CD134/OX40, CCR4, and CD30. Here we report immunohistochemical staining for CD69 in frozen and paraffin sections of peripheral T cell lymphomas that exhibit immunoreactivity for markers of Th1 or Th2 differentiation. CD69 expression correlated with immunoreactivity for other Th1 differentiation markers in 18 of 19 frozen specimens of peripheral T cell lymphomas (P = 0.0005). In 10 of these cases in which paraffin-embedded tissue was available for study, CD69 immunohistochemical staining of paraffin sections correlated with frozen section expression. CD69 immunostaining was performed on paraffin sections from 53 additional cases of peripheral T cell lymphoma and correlated with immunoreactivity for other Th1 differentiation markers (P < 0.0001) and was associated with specific subtypes of peripheral T cell lymphoma, including angioimmunoblastic lymphoma, Lennert's lymphoma, and mycosis fungoides/Sezary syndrome, previously noted to express Th1 differentiation-associated markers. Anaplastic large cell lymphoma, both systemic and cutaneous, which typically exhibits immunoreactivity for markers of Th2 expression, was negative for CD69 immunostaining in 22 of 24 cases. CD69 immunostaining results support previous findings that a subset of T cell lymphomas exhibits immunophenotypic features of either Th1 or Th2 T cell differentiation. In addition, CD69 is a useful immunohistochemical marker for specific T cell lymphomas in frozen and paraffin-embedded tissue.