(A) Expression of TCRBV segments by OS (▧) and a healthy age-matched infant (▪) PBMC. The data are expressed as the percentage of the color- imetric signal obtained with the individual TCRBV-specific probes. (B) Heteroduplex analysis of the indicated TCRBV chains’ PCR products of PBMC and thymocytes from the OS patient and the healthy control. On the right of each gel, monoclonal and polyclonal controls, prepared by loading in the gel the products obtained from TCRBV8-specific PCR amplification of the RNA of monoclonal (J77) and polyclonal (C1.632) cell populations,21 are shown.