Time course of specimen J (FL) xenograft development demonstrates abrupt plasma cell differentiation between 7 and 14 days. A total of 1 × 107 cells of specimen J were implanted in each of 6 mice; 2 mice were harvested at 2, 7, and 14 days (H&E stained). Ki67 staining was low at day 2, similar to the level in the original excised node (see insets on far right). Numbers of Ki67-positive cells increased by day 7, with a simultaneous increase in both T cells (CD2) and B cells (CD20). Between days 7 and 14, there was an abrupt loss of CD20 expression with appearance of CD138-positive forms. Note that CD138-positive forms were not present in the original biopsy (see inset). Tissue marked with asterisks are pancreas; original magnification of all images ×40.
