Flow cytometric determination of peripheral blood lymphocyte subpopulations and haematological values in the neonatal calf

Non-vaccinated Holstein female calves, 3–31 days old (n=106) were examined in order to determine peripheral blood lymphocyte subpopulations and haematological values. The relative populations of lymphocytes were determined using flow cytometry. Monoclonal antibodies were used to identify BoCD2⁺, BoCD4⁺, BoCD8⁺, B-cells,/ T-cells, and monocytes/neutrophils, respectively. Complete blood counts were also determined. Calves were stratified into four groups by age (days): group A = 3–7 days, group B = 8–14 days, group C = 15–21 days and group D = 22–31 days. Group A calves had 30%–70% lower numbers of all lymphocyte subtypes compared to older calves. Group B calves had significantly lower numbers of B-cells than calves in group D, but were not different from group C. Calves in groups B and C had significantly lower/ T-cell counts than calves in group D. All other group comparisons of lymphocyte subtypes and the ratios of BoCD4⁺ to BoCD8⁺ T-cells were not significantly different.Calves in group A had significantly lower white blood cell counts than older calves and had significantly lower lymphocyte numbers than group C and D calves. Calves in group D had significantly higher lymphocyte counts than younger calves. Groups A and B had significantly higher neutrophil to lymphocyte ratios than groups C and D. Absolute numbers of monocytes, eosinophils and basophils were not different among any of the groups. Group A calves had significantly lower red blood cell counts than older calves. Calves in groups A and B had significantly higher mean corpuscular haemoglobin (MCH) and mean corpuscular volume (MCV) values than calves in group C. Group C calves also had significantly higher MCH and MCV values than calves in group D. Significant differences in haemoglobin, haematocrit and mean corpuscular haemoglobin concentration values were not apparent among any of the four groups. In this cross-sectional study we observed that older calves consistently had higher numbers of all subtypes of peripheral blood lymphocytes, compared to younger calves.