Quantitative characterization of the CD5 bearing lymphocyte population in the peripheral blood of normal sheep.

Quantitative characterization of the circulating CD5+ lymphocyte population in sheep was performed using monoclonal antibodies against ovine CD5, ovine CD2, and ovine sIgM. A total of fifteen sheep were examined biweekly over a period of 2.5 months. The total CD5+ population was measured using single color flow cytometry, while CD5+ cells co-expressing sIgM or CD2 were determined by two color flow cytometric analysis. The total CD5+ cell population comprised 31.5-65.4% of gated lymphocytes with a mean value of 44.9%. Absolute CD5+ cell numbers varied from 1075 to 8007 cells mm-3, with a mean value of 3149 cells mm-3. The mean proportion of CD5+ B-cells was 4.0%, with a mean absolute value of 270 cells mm-3. The mean proportion of CD5+/CD2+ cells was 12.1% while that of CD5+/CD2- cells was 28.6%, corresponding to mean absolute values of 727 and 1794 cells mm-3 respectively. Significant variation in CD5+ lymphocyte numbers in all individual animals occurred over the time span of the study. The results of this study provide a baseline from which to accurately assess CD5+ cell populations in neoplastic and infectious diseases.