Interferon (INF)-α was the maintenance treatment of choice after autologous stem 
cell transplantation in multiple myeloma in the past, but currently Thalidomide 
is commonly used. In this prospective study, the implications of the various 
types of maintenance therapy on the patients T cell pattern and activation 
status were assessed. T cells were analyzed for expression of surface molecules, 
cytokine secretion, the presence of regulatory T cells, and the specific 
activation against the multiple myeloma antigen HM1.24. T cells from 69 multiple 
myeloma patients were analyzed: 19 patients were treated with IFN-α; 26 were 
treated with Thalidomide; and 24 patients received no maintenance therapy. 
Specific T cell activation with an immunogenic HLA-A2(+)-restricted peptide from 
the myeloma-associated antigen HM1.24 was impaired in the Thalidomide group. In 
accordance with this observation, there was a trend toward a higher amount of 
regulatory T cells in the Thalidomide group. Furthermore, patients treated with 
IFN-α showed high rates of naive T cells, whereas a high rate of effector memory 
T cells was observed in the Thalidomide group. Importantly, after cessation of 
Thalidomide therapy, this effect was reversible in the CD8 compartment. In 
conclusion, Thalidomide maintenance therapy has profound implications on T cell 
pattern and activation status, which compromise antigen specific antitumor 
immunity.