QUANTITATIVE CHARACTERIZATION OF LYMPHOCYTE POPULATIONS IN BRONCHOALVEOLAR LAVAGE FLUID AND PERIPHERAL-BLOOD OF NORMAL ADULT ARABIAN HORSES

Bronchoalveolar lavage fluid (BALF) and peripheral blood were obtained from each of 17 adult Arabian mares and absolute numbers and relative lymphocyte proportions were determined for total T lymphocytes, using CD2 as a marker, CD4 + T lymphocytes, CD8 + T lymphocytes, CD5 + lymp hocytes, and sIgM + B lymphocytes. The marked variation in BALF cell r ecovery resulted in wide variation in absolute values for each lymphoc yte subset. The relative proportions of gated BALF lymphocytes were mu ch less variable and provided a basis for comparison of lymphocyte sub sets between the BALF and peripheral blood in normal horses. The total lymphocyte population was comprised predominantly of T cells in both BALF (83 +/- 11% CD2 + lymphocytes) and peripheral blood (70 +/- 8% CD 2 + lymphocytes). There was a significantly greater percentage of tota l T lymphocytes and a significantly lower percentage of B lymphocytes in BALF as compared with peripheral blood collected at the same lime. The increase in total T lymphocytes in BALF reflected a significantly higher percentage of CD8 + T lymphocytes in BALF (39 +/- 7%) as compar ed with peripheral blood(18 +/- 5%). The mean percentages of CD4 + T l ymphocytes (58 +/- 13% in BALF; 62 +/- 8% in peripheral blood) and CD5 + lymphocytes (78 +/- 11% in BALF; 71 +/- 7% in peripheral blood), a population composed primarily of T lymphocytes but also including a su bset of sIgM + B lymphocytes, were not significantly different between the two compartments. These normal values in Arabian mares provide a basis for detection of disease associated changes in the lymphocyte po pulations and for determination of effects of age and breed on lymphoc yte subpopulations in the BALF and peripheral blood.