Multicolor cytoenzymatic evaluation of dipeptidyl peptidase IV (CD26) function in normal and neoplastic human T-lymphocyte populations

Phillip Ruiz, Natalia Zacharievich, Mark Shenkin

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Dipeptidyl peptidase TV (DPP IV), also identified as the glycoprotein CD26, is a transmembrane 110- to 120-kDa serine aminopeptidase involved in immune responses by influencing T-cell costimulation and by cleaving cytokines. Additionally CD26 is a nonintegrin receptor that contains a binding site for extracellular matrix and other molecules. In order to further define the expression and functional activity of this membrane exopeptidase in human T cells, we developed a nondisruptive, four-color cytofluorogenic assay that utilizes three separate antibodies to cell-surface molecules (e.g., CD4/CD8/CD26 and CD19/CD56/CD26) along with a rhodamine 110-conjugated dipeptide substrate that allows the measurement of DPP TV activity in phenotypically defined cells. We found normal human thymi to have notable differences in time-dependent DPP IV activity among the thymocyte subsets defined by their CD4/CD8 phenotype, with CD4-/CD8- thymocytes containing less DPP IV activity than cells expressing CD4 and/or CD8 (i.e., maturing). CD26 positivity was moderately intense in thymocytes and tended to identify cells with higher DPP IV activity. The four-color technique was also used to examine mature peripheral blood lymphocytes, along with an assortment of leukemias and transformed T-cell lines. These experiments revealed that while DPP IV was consistently evident in normal T cells, neoplastic T cells could vary in their expression patterns. Furthermore, the presence (or intensity) of surface CD26 in some abnormal T cells and certain normal peripheral blood mononuclear cells was separable from the level of DPP IV measured intracellularly. Our results established that multicolor cytofluorographic analysis can be a practical means to measure DPP IV activity in various human cell populations. Furthermore, we found that DPP IV activity could vary in T cells according to their differentiation status and that under certain circumstances surface CD26 expression can be disassociated from the level of measured enzyme (i.e., DPP IV) activity.

Original languageEnglish (US)
Pages (from-to)362-368
Number of pages7
JournalClinical and Diagnostic Laboratory Immunology
Issue number3
StatePublished - 1998

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology
  • Clinical Biochemistry
  • Microbiology (medical)


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