Jacalin: an excellent lectin for obtaining T cell growth activity from rat spleen cells

1. The parameters involved in the choice of an optimal T cell growth activity (TCGAc) induction protocol using rat spleen cells stimulated with jacalin were studied. 2. In the absence of serum, 5 micrograms/ml jacalin was sufficient to obtain maximal TCGAc. Supernatants could be harvested at any time between 24 and 72 h since significant consumption of TCGAc was not observed during this interval. TCGAc recovery was increased in the presence of 5% fetal calf serum, with the optimal jacalin dose being about 25 micrograms/ml. The recommended harvesting time was 24 h to reduce TCGAc loss due to cellular proliferation. 3. Human or rat sera were not suitable since they absorb significant amounts of jacalin, thus shifting the optimal lectin concentration to greater than 800 micrograms/ml. Indomethacin (1 micrograms/ml) had little enhancing effect on TCGAc production by rat cells but rendered conditioned media less inhibitory of cytotoxic T lymphocyte L (CTLL) proliferation. Addition of 50 ng/ml phorbol myristate acetate is not recommended if the supernatants are to be used for T cell line maintenance, since the agent interferes with CTL function, while only doubling TCGAc production. 4. Jacalin-stimulated TCGAc recovery is comparable, in titer, to that obtained with concanavalin A under the best conditions, but the former is less expensive due to the large quantities of lectin recovered from a single jackfruit, besides being less toxic for rat spleen cells.