H2AX and lymphoma: To further investigate the levels of proliferation and DNA damage accumulation in pre-neoplastic (not affected by lymphoma) tissues in these mice, primary splenocytes and bone marrow cells from ESPL1+/hyp, p53−/−, p53−/− and WT mice at the average age of three months (not affected by lymphoma) were stained for Ki67 and gamma H2AX markers.