High frequency of CD45RO expression in AIDS-related B-cell non-Hodgkin's lymphomas

Although immunophenotypic abnormalities have been reported in B-cell non- Hodgkin's lymphomas (NHLs) occurring in the general population, there are no extensive studies on such abnormalities in AIDS-related B-cell NHLs. Reactivity of CD45RO/UCHL1 and expression of other T-cell associated antigens (CD43, OPD4, CD3, CD5, EMA) were examined by immunohistochemistry in 66 diffuse aggressive AIDS-related B-cell NHLs and in 296 AIDS-unrelated B-cell NHLs of similar morphology analyzed in the same institution. EBER in situ hybridization studies were also carried out in 57 of the 66 AIDS-related B- cell NHLs investigated. CD45RO/UCHL1 was expressed in 27% of AIDS-related B- cell NHLs, but only in 8% of diffuse aggressive AIDS-unrelated B-cell NHLs. The difference was highly significant (P <.001) overall and, within the Working Formulation subtypes, especially marked among small noncleaved cell (SNCC) lymphomas. Conversely, the reactivity of other T-cell associated antigens seemed to be very similar in AIDS-related and AIDS-unrelated NHLs. However, for CD43, a significantly lower number of positive cases was found in AIDS-related NHLs among SNCC lymphomas. Among AIDS-related B-cell NHLs, the highest frequency of CD45RO/UCHL1 expression was found in the immunoblastic subset with plasmacytoid differentiation. In the latter CD45RO/UCHL 1 preferentially associated with EMA expression and EBV infection of the tumor clone, but not with CD45RA. The present finding of an excess of CD45RO/UCHL1 expression in AIDS-related B-cell lymphomas may reflect the preferential expansion of CD45RO expressing B-cell clones with putative autoreactive potential, as suggested by the expansion of CD45RO expressing B- cells in auto-immune disorders.