The present study was undertaken to establish reference values for the composition blood
lymphocyte populations and compare forty three Hanwoo neonatal calves (KC) with twenty one Holstein
calves (HC) by blood cell count and immunophynotying. The percentages of CD2+, CD4+, CD8+, CD26+,
ACT2+, MHC class, MHC class II and WC1+ T cells, B cells were determined by flow cytometry. The
number of lymphocyte and monocyte in HC were higher than those of KC. However, the number of
neutrophils was higher in HC than KC. The proportions of CD2+, CD4+, CD8+, MHC class, and WC1+
lymphocytes remained relatively stable during the study period, while there was a moderate increase in
the relative percentage of CD26+, ACT2+, MHC class II and B cell from birth to approximately 3 weeks
of age. Marked differences in the relative proportions of the lymphocyte subpopulations were noted between
the individual calves. The present study shows that the T-cell subpopulations are present in peripheral blood
of KC at levels comparable with HC, while the MHC class II and B cell population of KC increases
significantly with age. The absolute number of WBC in KC was due to the decrease of absolute number
of neutrophil rather than the increase of lymphocyte. The results indicated that KC have significantly higher
number of neutrophils, and proportion of MHC class II and B cell than HC.