Rat immunoglobulin genes have comparable patterns of JH rearrangement in normal peripheral B cells and in pre-B and cultured TdT+ cells from bone marrow.
Pre-B cells from normal rat bone marrow were isolated by first rosette-depleting granulocytes, T cells and stem cells with W3/13 mAb and mature B cells with anti-Ig mAb, and then in some samples enriching by FACS-sorting HIS24+ cells. Presumptive precursors of these pre-B cells possessing terminal deoxy-nucleotidyl transferase were prepared by culture of normal marrow. The extent of rearrangement of kappa and heavy chain genes was estimated on both these types of cells and on mature peripheral B cells by measuring the disappearance of the germ-line restriction fragments encoding J segments (other than JH1) relative to a non-rearranging CK fragment. Pre-B cells and B cells showed similar degrees of rearrangement of their kappa genes, leaving roughly half in germ-line form; the TdT+-enriched cells showed approximately similar heavy chain rearrangement as the peripheral B cells. Some non-germ-line restriction fragments hybridising with JH in sufficient amount to register as discrete bands on Southern blots were found in common between these different cell populations taken from different individual donors. These may represent preferred D-JH or perhaps V-D-JH rearrangement arising repetitively in independent clones, or may be due to dominance by a few preferred clones.