RAG1 AND RAG2 IN DEVELOPING RABBIT APPENDIX SUBPOPULATIONS

The appendix of young rabbits is a site of primary heavy chain variabl e region-gene diversification and B cell selection. Appendix cells fro m 6- to 9-wk-old rabbits were stained and sorted for surface CD43 and IgM. We found that the CD43(+)IgM(-) and double-negative CD43(-)IgM(-) cells contained RAG1 transcripts and RAG2 protein, The presence of RA G gene products in appendix raised the possibility that pro-/pre-B cel ls were present in young rabbit appendix, Although an early suggestion that RAG2 plays a role in variable region-gene diversification by gen e conversion in chicken bursa was not supported by studies of RAG2 pro tein in this tissue, we produced anti-rabbit RAG2 Abs to determine whe ther RAG2 protein was present in rabbit appendix, where cells that rec ently underwent gene conversion are found, We detected RAG2 protein in the four subpopulations of rabbit appendix lymphocytes, distinguished by surface CD43 and IgM markers, The appearance of RAG gene products during different stages of B cell maturation may reflect the function of the young rabbit appendix as a site of both B cell development and diversification.