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
1	6/30	4×Vκ1–9	Vκ3–11	4/6
		2×VH4–34	VH3–66
3	14/30	5×Vκ1–17	Vκ4–1	12/14
		9×Vκ2D–28	Vκ1D–39
6	6/15	6×VH1–69		6/6

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.