Kinetics of the plasma cell compartment in peripheral blood from a patient with a bacterial infection. Days after hospital admission are indicated. Peripheral blood CD19+ lymphocytes were gated and stained for expression of CD27 in combination with CD20 or CD138 expression. Plasma cells were identified as (A) CD27++/CD20− cells and (B) CD27++/CD138+ cells. Frequencies of CD27++ plasma cells were established at day 0, 1, 2, 4, and 8 after hospital admission. At day 4 of hospitalization, an expansion peak of plasma cells is seen.