Southern blots of variable region heavy chain(VH) immunoglogulin gene PCR-products of two synovial membranes and peripheral blood from one patient with rheumatoid arthritis undergoing synovectomies of several finger joints. (a) Framework region (FR)-3 hybridization. (b) and (c) Motif-specific complementarity determining region (CDR)-3 hybridizations. (a) Lanes represent the blotted 350 base pair PCR products in the order of the respective VH family for peripheral blood (B) and two synovial membranes (S1, S2). Distinct VH6 bands of the same height in the FR3 hybridization were thought to represent recirculating, clonally-related genes. This was confirmed by hybridization with motif-specific probes for the respective CDR-3. After 'stripping' with boiling water, the membrane was consecutively rehybridized. (b) Hybridization to the CDR3A-motif occurred at the same height on the VH6-lane of S1 and S2, confirming the presence of the same B-cell clone in both joints (triangle). (c) One VH6 gene from S1 represents the CDR3B-motif (circle).