Dipeptidylaminopeptidase IV activity in T lymphocyte subsets in B cell non-Hodgkin's lymphomas

CD26/dipeptidyl peptidase IV expression in human lymphomas is restricted to CD30-positive anaplastic large cell and a subset of T-cell non-Hodgkin's lymphomas

CD26 is identical to the cell surface ectoenzyme dipeptidyl peptidase IV (DPPIV). CD26/DPPIV is associated with T-cell activation and proliferation and also may function as an auxiliary adhesion factor. Although CD26/DPPIV has been previously studied on lymphoid populations and on leukemias/lymphomas of B- and T-cell phenotype, little is known about its expression and functional role in some specific types of lymphomas, such as CD30-positive anaplastic large cell (ALC) lymphomas and Hodgkin's disease (HD). A series of 81 lymphoma samples, including 23 cases of HD, 17 cases of CD30-positive ALC lymphomas, 41 cases of other non-Hodgkin's lymphomas (NHL), and a panel of HD- or ALC lymphoma-derived human cell lines were evaluated for CD26/DPPIV expression by enzyme histochemistry and immunohistochemistry on frozen sections and cell smears. CD26/DPPIV protein was expressed on neoplastic cells in 12 of 17 (71%) ALC lymphomas irrespective of their antigenic phenotype and in seven of 15 (47%) T-cell NHLs. In contrast, we did not detect CD26/DPPIV expression in tumor cells from 26 cases of B-cell NHL other than ALC lymphomas or in Reed Sternberg (RS) cells and variants of 21 of 23 HD cases. Accordingly, CD26/DPPIV expression was maintained on the CD30-positive ALC lymphoma cell line Karpas 299, but the molecule was not detected on HD-derived cell lines of B, T, or non-B non-T phenotype. These results may support a new potential tool for the phenotypic separation of ALC lymphomas from HD based on the differential expression of the CD26/DPPIV molecule. Moreover, given the demonstration that CD26/DPPIV is identical to the human adenosine deaminase (ADA) binding protein, it could be speculated that CD26/DPPIV also may function by interacting with ADA to regulate the growth of CD26/DPPIV expressing neoplastic cells in ALC lymphomas.

Immunohistocytochemical correlation of DAP IV-CD 26 reactivity with immunologic markers of lymphocyte activation in human lymphoid tissues

The topographic distribution of the dipeptidylaminopeptidase IV (DAP IV-CD 26) and II (DAP II) positive T-cell population in six reactive lymph nodes and seven follicular B-cell non-Hodgkin's lymphomas (NHL) was analysed with regard to the distribution of activated T-cells, as visualized by a panel of monoclonal antibodies including Tac-CD 25, HLA-DR, OKT 9-CD 71, ICAM-1-CD 54, LFA-1-CD 11a. For comparative studies serial frozen sections of the lymph nodes were tested by enzyme histochemistry and immunohistochemistry. In addition, cell suspensions obtained from 10 B-NHL and interleukin-2 (IL-2) activated T-cells were investigated by a combined cytochemical and immunological method for simultaneous visualization of DAP IV-CD 26 cytoplasmic activity and surface immunostaining for markers of lymphocyte activation. Both in reactive and lymphomatous lymph nodes the topographic distribution of DAP IV-CD 26+ and DAP II+ lymphocytes was rather similar to that of Tac-CD 25+ lymphocytes. On the contrary, the DAP IV-CD 26 and DAP II distribution pattern substantially differed from that of the other immunologic markers. In a cell suspension of IL-2 activated T-cells, more than 80% of the cells with a blastic morphology were DAP IV-CD 26+; DAP IV-CD 26+ cells coexpressing Tac-CD 25, OKT 9-CD 71, HLA-DR positivity, relative to the total number of DAP IV-CD 26 positive cells, were 90.5%, 70.5% and 87% respectively. Only small (not activated) lymphocytes expressed a focal cytoplasmic DAP II positivity. In cell suspensions from 10 cases of B-NHL the mean percentage of DAP IV-CD 26+ Tac-CD 25+ cells was 75.8. Only a small number of DAP IV-CD 26+ cells coexpressed HLA-DR, the mean percentage being 9.6. The results support the view that DAP IV-CD 26 may be considered as a marker of lymphocyte activation; this marker seems to be restricted to T lymphocytes that reside in the T dependent areas of reactive lymph nodes and to non malignant T-cells surrounding neoplastic follicles of follicular NHL.