Abstract
The enzyme‐linked immunospot (ELISPOT) assay has become a widely employed method for quantification of antigen‐reactive T lymphocytes. In recent years, various types of antigen‐presenting cells (APCs) have been tested as stimulator cells in ELISPOT protocols to achieve a highly sensitive and rapid assay which is not impaired by a marked nonspecific cytokine release. However, the currently available APCs still have disadvantages, such as significant background reactivities, limited sensitivity, and time‐consuming preparation procedures. Recently, we succeeded in defining a novel subpopulation of circulating dendritic cells (DCs) that can easily be prepared from human blood. These M‐DC8+ DCs proved to be very effective in the induction of antigen‐specific T cell responses. In the present study we provide evidence that M‐DC8+ DCs are particularly well suited as APCs for the detection of antigen‐specific CD8+ T cells after challenge with viral or tumor peptides in ELISPOT assays. In addition, protein‐loaded M‐DC8+ DCs proved to be quite efficient in the presentation of MHC class II‐bound peptides, thus allowing the determination of frequencies of antigen‐reactive CD4+ T cells. The use of M‐DC8+ DCs as stimulator cells can improve the ELISPOT assay by combining high sensitivity, rapidity, and low background reactivity. J. Clin. Lab. Anal. 16:30–36, 2002. © 2002 Wiley‐Liss, Inc.