A RISE IN THE PERCENTAGE OF LARGE UNSTAINED CELLS IN THE PERIPHERAL-BLOOD DETERMINED BY THE HEMALOG-D90 AUTOMATED DIFFERENTIAL COUNTER IS A FEATURE OF IMPENDING MYELOID ENGRAFTMENT FOLLOWING BONE-MARROW TRANSPLANTATION

Summary The early phase of bone marrow regeneration has been monitored by automated differential counts on the peripheral blood using a Hemalog D90, following 107 transplant procedures. An elevated percentage of large unstained cells (LUCs) was detected in over 98% of cases and in 72% of cases the rise in percentage LUCs preceded the rise of the total leucocyte count into the detectable range on a Coulter counter (> 0.3 × 109/l) by an average of 4 days. These LUCs are shown to be CD8+T lymphocytes. The ability to detect the earliest signs of regeneration is particularly useful when regeneration is delayed and repeat marrow infusion is considered.