T and B lymphocytes in horses persistently infected with equine infectious anaemia virus.

The percentage of T and B lymphocytes in the peripheral blood of horses chronically infected with equine infectious anaemia (EIA) virus was determined and the results were compared with the percentage of these cells in healthy uninfected horses. Cells with membrane receptors for sheep erythrocytes (T and active T lymphocytes) were determined by E and A rosette techniques, while cells with receptors for the C3b component of complement and those with receptors for mouse erythrocytes (B lymphocytes), were determined by the EAC rosette method. The percentage of Fe positive cells was assayed by the EA rosette test. The majority of peripheral blood lymphocytes (PBL) from both uninfected and EIA-infected horses formed rosettes of each kind with only three erythrocytes indicating a low density of the corresponding receptors on the cell membrane under the condition of the assays used. The percentage of T lymphocytes in the peripheral blood of diseased horses (52.4 +/- 1.6%), as detected by E rosettes, was significantly (p less than 0.01) higher than in control animals (42.4 +/- 3.5%). In clinically healthy horses 8.9 +/- 1.1% of PBL were identified by A rosettes as active T cells, whereas animals with a chronic form of EIA had a much lower (p less than 0.001) percentage of these cells (4.7 +/- 0.7%). In the B lymphocyte subpopulations the percentages of cells bearing Fc and C3b receptors were markedly elevated (p less than 0.001) in EIA-infected horses (24.7 +/- 0.8% and 42.8 +/- 2.2% respectively) as compared to uninfected animals (15.1 +/- 1.4% and 29.6 +/- 1.2% respectively).(ABSTRACT TRUNCATED AT 250 WORDS)