Karyotype of a mouse/rabbit hybrid clone secreting rabbit immunoglobulin x light chain

A mouse/rabbit hybrid clone producing a rabbit immunoglobulin x light chain of allotype b4 is described. After one year in culture the clone is still producing the rabbit x chain and carries all the chromosomes of the mouse parental cell and one rabbit chromosome, No. 15. On two occasions, one month apart, this chromosome was present in 80% and 100% of the mitoses. Three hybrid lines not producing rabbit immunoglobulin chains did not carry any rabbit chromosomes.