Evaluation of CD229 as a new alternative plasma cell gating marker in the flow cytometric immunophenotyping of monoclonal gammopathies.

Background: Current flow-cytometric plasma cell (PC) gating is based on CD138, CD38, and CD45 expression. CD138 is known for variable expression and loss during storage and processing. Introduction of anti-CD38 and anti-CD138 monoclonal-antibody therapies has limited the use of these markers during follow-up.