The effect of bone marrow regulatory peptides on antibody production by hybridoma cells.

Peptides produced by bone marrow cells (myelopeptides) increase antibody production. Since antibody producing cells seemed to be their targets, we tested in these experiments the effect of myelopeptides on antibody production by 2B2 and 2C12 hybridoma cells. Both hybridomas produce anti-SRBC monoclonal antibodies of the IgM class. The 2B2 cells do not produce direct haemolytic plaques and less than 5% of them produce the indirect ones during the 90-min assay period. When they were cultivated with myelopeptides for 15 h, the number of indirect plaques increased two-fold. A slightly lower increase was observed after 24 h of incubation, while the 48-h incubation period did not increase the number of detected plaques. After 6 h of preincubation, only a slight increase in indirect plaque numbers was observed. About 25% of the 2C12 hybridoma cells produce both direct and indirect haemolytic plaques during the assay period. The effect of myelopeptides was studied only on the indirect ones and no clear effect was observed. Only after the 15-h incubation period a slight increase in plaque numbers was observed. Because the myelopeptides affect antibody production of hybridoma cells, antibody producing cells are evidently the targets of these substances. It remains to be established, whether they are the only target cells in the myelopeptide action on the immune response.