Clonality of the immunoglobulin heavy chain genes in B cell non-hodgkin lymphoma using semi-nested PCR

Identification of gene rearrangements and clonality analysis are important techniques for the diagnosis of malignant lymphoproliferative diseases. These methods have various sensitivities based on the type of primer used and method of determination of polymerase chain reaction (PCR) products. This study aimed at determining the clonality of B cell non-Hodgkin lymphoma in Iranian patients using PCR method and 2 primers of FR2 and FR3.

Paraffin embedded blocks of 67 patients with B cell lymphoma and 19 cases with lymphoid hyperplasia of the lymph nodes who presented to NRITLD, Masih Daneshvari Hospital were retrospectively reviewed. After extracting the genomic DNA using phenol and chloroform, clonal analysis was performed using semi-nested PCR by using two primers: FR2 and FR3. PCR products were determined using 2 techniques of heteroduplex analysis, polyacrylamide gel and silver staining and the conventional method of agarose gel and ethidium bromide staining. Appearance of 1 or 2 bands in the desired location were considered as a sign of clonality.

Monoclonal gene rearrangement was observed in 62 out of 67 patients (92.5%) as one or two discrete bands appeared within 60-120 base pairs (bp) and 200-300 bp range. Of the mentioned patients, 53 cases (79.1%) had FR2 and 51 (76.1%) had FR3 rearrangement. Heteroduplex analysis along with silver nitrate staining detected 3 out of the remaining 5 cases of lymphoma to be monoclonal. These cases had been reported negative by the conventional technique. In total, 65 out of 67 patients (97%) showed monoclonal gene rearrangement using both the abovementioned techniques. All hyperplasia cases were polyclonal by this method.

Our study showed that evaluation and detection of clonality using PCR, FR2 and FR3 primers along with heteroduplex analysis is a rapid sensitive technique for the diagnosis of malignant lymphomas.