Identification oflymphocyte subsets inthenewborn using a variety ofmonoclonal antibodies

SUMMARY Using a small sample ofperipheral venous blood, thenormal rangeforlymphocyte subpopulations (T-cell, B-cell, T-suppressor cell, andT-helper cell) was defined innon-infected pretermandterminfants. Lymphocyte subsets wereidentified using avariety ofmonoclonal antisera, andanalysis was performed using a fluorescent activated cell sorter. Suchmethods allow an objective assessment ofabsolute numbers ofcells perunitvolumeofwholeblood. There was no significant difference inabsolute numbers oflymphocyte subsets between termandpreterm appropriate forgestational age(AGA)infants. Infants whoweresmall forgestational age(SGA)hada significant deficiency inabsolute numbers oftotal T-cells, helper andinducer T-lymphocytes, and B-cells compared withbothtermandpreterm AGA infants. Allnewborn infants (term andpreterm; AGA andSGA)hadahighly significant increase inabsolute numbers ofbothhelper andsuppressor T-lymphocytes compared withnormal adults. Itiswellknownthatthetotal lymphocyte countis increased inthenewborninfant compared with adults.' Thepercentage ofT-lymphocytes inthe newborn defined byrosetting withsheep erythrocytes hasbeenvariously reported asnormal ordecreased inhealthy terminfants, although theabsolute values arecomparable with, orhigher thanadult values.2 Several authors haveshownthatboththepercentage andabsolute numbers ofB-lymphocytes are increased inneonates.3 Otherstudies indicate that thepercentage ofB-cells islowerinneonates, butagreethattheabsolute numbers arehigher taking intoaccount theincreased total lymphocyte count.2 4Onestudy compared preterm (5infants, gestational agerange28to36weeks) withterm infants, butcould shownosignificant difference in thenumbers ofT-orB-cells.3 Ninepreterm infants werestudied byHallberg andHallberg,5 and4 showed adecreased percentage ofE-rosette forming cells inthefirst fewdays oflife compared with adult controls. Byage3weekshowever, thepercentage in all infants hadreached adult levels. Themethodofseparation ofhumanlymphocytes fromerythrocytes andgranulocytes canconsiderably biastheproportion ofT-andB-lymphocytes and mayaccount fortheapparent differences obtained byothers. We havefoundficoll-hypaque gradient centrifugation to be unreliable, particularly in