CD38 and CD138 can be used as markers for plasma cells.
Robillard, N., Wuillème, S., Moreau, P., & Béné, M. C. (2014). Immunophenotype of normal and myelomatous plasma-cell subsets. Frontiers in immunology, 5, 137.
iFluor® 450 Anti-human CD38 Antibody *HB7*
iFluor® 594 Anti-human CD138 Antibody *MI15*