In vitro dendritic cell generation and lymphocyte subsets in myeloma patients: influence of thalidomide and high-dose chemotherapy treatment

Abstract

While vaccination with antigen-pulsed dendritic cells (DCs) represents a promising therapeutic strategy in multiple myeloma (MM), clinical benefit, so far, has been limited to individual patients. To identify potential problems with this approach, we have analyzed the influence of treatment parameters, in particular high-dose chemotherapy (HD-CTX) and thalidomide, on in vitro DC generation and peripheral blood lymphocyte subsets in MM patients. From a total of 25 MM patients, including 14 patients on thalidomide treatment and 11 after HD-CTX, in vitro DC generation from peripheral blood monocytes under serum-free condition was investigated. In addition, peripheral blood lymphocyte subsets were assessed in 17 patients including 10 patients on thalidomide treatment and 9 patients after HD-CTX. Efficient in vitro generation of DCs (median 7.1x10(6)/100 ml peripheral blood; range 0.1-42.5x10(6)/100 ml peripheral blood) expressing DC-typical surface markers was observed in 23 MM patients (92%), although reduced expression of CD1a, CD40, CD83, and HLA-DR was observed in patients treated with thalidomide. With respect to lymphocyte subsets, MM patients showed significantly (p<0.05) reduced B and CD4+ lymphocytes in the peripheral blood. This effect was most prominent within 6 months of HD-CTX and in patients receiving thalidomide (usually in combination with CTX). CD8+ lymphocytes were significantly increased in MM patients. Thus, despite the well-known deficiencies in their immune system, adequate numbers of DCs can be generated in most myeloma patients. In patients treated with thalidomide, however, it remains to be seen whether the reduced expression of co-stimulatory molecules has functional relevance.

Fig. 1

Surface phenotype of in vitro-generated DCs. Median values (bold lines) and interquartile ranges (boxes) of mean fluorescence intensity (MFI) for surface expression of CD1a, CD14, CD40, CD83, CD86, and HLA-DR of mature DCs (day 14) are depicted. Whiskers shown above and below the boxes represent the largest and smallest observed scores that are less than 1.5 box length from the end of the box, i.e. in practice, the lowest and highest values expected. Data are given for mature DCs from myeloma patients with (+Th) and without (−Th) thalidomide treatment in comparison with DCs from healthy volunteers (Co). * Denotes significant differences (p<0.05) to healthy volunteers, # denotes significant differences (p< 0.05) to myeloma patients without current treatment with thalidomide.