Cell-mediated immune response to Babesia equi-transformed lymphoblastoid cells in vitro.

The capacity of equine peripheral blood lymphocytes (PBL) to proliferate in the presence of Babesia equi-transformed lymphoblastoid stimulator cells was tested in an autologous as well as in an allogenic one way mixed lymphocyte reaction (MLR). It was found that both autologous and allogeneic responder lymphocytes incorporated high amounts of 3H-thymidine. The incorporation of 3H-thymidine was lower in MLR using as stimulator cells lymphocytes from which the cell line had previously been established, than when using parasitized culture cells as stimulator. Proliferation of PBL was achieved only with intact infected cells, whereas sonified lymphoblastoid cells did not have this effect. During the course of an infection with B. equi, PBL from six ponies were tested for their capacity to inhibit the in vitro growth on culture cells, when applying cell co-cultivation. Starting from day 18 p.i., PBL from older animals inhibited culture schizont growth more effectively than PBL from young ponies. On day 35 p.i., only PBL from two of the older ponies showed an inhibitory effect. Influences of effector cells on target cells and possible mechanisms of their recognition are discussed.