Neoplasms arising in CBA mice after transfer of spleen cells from syngeneic old donors.

Young (15-week-old) CBA/Ca mice were injected intravenously with spleen cells from individual young (15-week-old) or old (18-24-month-old) CBA/T6T6 mice. Samples of peripheral blood were taken at monthly intervals and cultured with phytohaemagglutinin (PHA) to stimulate T lymphocytes into mitosis. In the recipients of young lymphocytes, the percentage of donor cells dividing in these cultures remained low throughout the experiment, but in the recipients of old spleen cells, after an initial period when the percentage of donor cells declined, there was a marked increase in the percentage of donor cells. The interval between the injection and the increase in the proportion of donor cells was very variable. Ten of the 12 recipients of old lymphocytes developed tumours involving the spleen and mesenteric lymph node. They resembled type B reticulum cell neoplasms as described by Dunn & Deringer (1968), and all but two were transplantable. In addition, one mouse that had no evidence of tumour on histological examination nevertheless gave rise to a transplantable tumour. The five tumours on which chromosomal analysis was carried out proved to be of old donor cell origin. Two out of the five recipients of young cells also eventually developed tumours, but these arose later than the others, had a more granulocytic character, and did not transplant.