CD28 and plasma cell myeloma: In untreated myeloma patients, a slight increase of CD27−/28− T-cells to a mean fraction of 13.6% (± 4.13) and decrease of CD27+/CD28+ T-cells to a mean fraction of 75.2% (± 4.53) in comparison to healthy donors could be demonstrated (p=0.02 and p=0.013, respectively).