Table 1

Analysis of V gene rearrangements of micromanipulated L&H cells

Case	Cells positive in PCR	Repeatedly amplified rearrangements	Unique rearrangements	Clonally related cells
Taking the results from all three cases together, most micromanipulated cells (22 of 26) were clonally related and thus belong to the L&H cell tumour clones. The fraction of clonally unrelated V gene rearrangements is in the same range as previously seen when micromanipulated cells were identified by immunohistochemical staining, showing that L&H cells were reliably identified based solely on morphology. Although the fraction of clonally unrelated B cells was low, these cells could cause false positive results if most of them were centroblasts expressing large amounts of AID. However, in lymphocyte predominant HL, centroblasts form only a minor fraction of the B cells. Furthermore, in case 3, where about 15% of cells carried unique V gene rearrangements, AID expression was not detected in the L&H cells, indicating that the contaminating cells did not result in false AID positivity.
In our analysis we found no intraclonal diversity, although case 1 showed intraclonal diversity in a previous analysis.³ This may be because of the low numbers of rearrangements analysed and because two of the V_κ rearrangements (V_κ1–9 in case 1 and V_κ1–17 in case 3) were unmutated, and hence probably exempt from somatic hypermutation by inactivation of the Ig_κ locus.
AID, activation induced cytidine deaminase; L&H, lymphocytic and histiocytic; PCR, polymerase chain reaction.
1	6/30	4×V_κ1–9	V_κ3–11	4/6
		2×V_H4–34	V_H3–66
3	14/30	5×V_κ1–17	V_κ4–1	12/14
		9×V_κ2D–28	V_κ1D–39
6	6/15	6×V_H1–69		6/6