Clonotypic cells are frequent in the BM of MM-engrafted mice.

Mice engrafted IC with cells from patient 5 (A), and a mouse injected IO into the sternum with cells from patient 1 (B) were killed at the time of end stage disease, followed by harvest of the femoral bone marrow. The number of clonotypic cells engrafting the femurs was determined by a cellular limiting dilution RT-PCR, as described in “Materials and Methods.” In a replicate dilution series, primers to histone were used to determine the number of tubes having intact mRNA. For patient 5, tumors from 3 different engrafted mice were dispersed through a sieve and the cells deposited at limiting dilution into PCR tubes; the phenotypic analysis of the tumor from mouse 5a is shown in Figure 1. Because the PCR is a direct lysis method, aliquots having 1000 cells per tube sometimes exhibit less PCR product that tubes having fewer cells, presumably because of cellular proteins compromising the PCR reaction. The extent to which this occurs appears to depend on the source of cells being deposited into the tubes.