Effect of plant lectins on murine myeloma cells.

The mitogenic response (determined by uptake of [3H]-thymidine) of two different BALB/c myeloma lines, normal BALB/c spleen cells and spleen cells from tumour-bearing mice in primary culture to PHA, Con A, PWM and Robinia pseudoaccacia (RPA) extract was determined by measuring the uptake of [3H]-thymidine over 96 h. The pattern of the response of tumour and tumour-spleen cells to the 4 different lectins was similar, and different from that of normal spleen cells. The unstimulated cultures of tumour and tumour-spleen cells displayed an initial increased uptake of [3H]-thymidine, whereas stimulated cultures displayed a low initial uptake of label. After an initial phase of inhibition, ADJ-PC5 myeloma cells were stimulated by PHA and PWM to a greater extent than were normal spleen cells. On the other hand, normal spleen cells gave a markedly better response to Con A and RPA. The mitogenic response of tumour-spleen cells to all 4 lectins was intermediate between those observed for tumour and normal spleen cells; they responded better to Con A and RPA than did tumour cells but were not as responsive as spleen cells, whereas the converse was true for their response to PWM and PHA. In agreement with other reports, the data suggest that the responsiveness of tumour-spleen cells was due to the presence of tumour cells in this tissue. These results indicate that there is no definite evidence of an impaired lectin-responsiveness in lymphoid cells of mice bearing a myeloma.