Murine lymphocytes preactivated with mitogen (both T and B) produce soluble transmitters which stimulate cytostatic activity of normal mouse bone marrow cells, tested by in vitro inhibition of P815 mastocytoma and L1210 lymphoma cell growth. 7-Interferon is one of T-cell products stimulating antitumor activity of bone marrow cells. Cytostatic activity stimulated by T-cellular soluble transmitters is another characteristic of bone marrow cells isolated from nude mice.
Key Words: T, B lymphocyte; bone marrow cell; tumor growth inhibitionBone marrow cells (BMC) similar by many phenotypical signs to bone marrow natural suppressor cells suppress the growth of leukemic cells in vitro [1,2,[8][9][10]. Tumor growth suppression by BMC does not involve tumor cells destruction and is mediated, at least partially, by soluble cytostatic products [9]. We studied the capacity of activated T and B lymphocytes to regulate cytostatic activity of BMC by producing soluble products.
MATERIALS AND METHODSThree-six-month-old (C57BL/6xDBA) F 1 (BDF1, H-2b/H-2 ~) mice from Breeding Center of Siberian Division of Russian Academy of Medical Sciences, and nude BALB/c nu+/nu + mice from the Department of Experimental Biomedical Simulation, Tomsk Research Center, Russian Academy of Medical Sciences, were used. The animals received sterilized fodder and acidified (pH 2.8) boiled water. P815 mastocytoma (H-2 ~) and L1210 lymphoma (H-2 a) cells were obtained from the Oncology Research Cells were cultured in RPMI-1640 with 2 g/liter NaHCO 3, 10 mM HEPES, 2 mM L-glutamine, 5x 10 -5 M 2-mercaptoethanol, antibiotics, and 7% fetal calf serum (all reagents from Sigma) in a humidified atmosphere with 5% CO z.Splenocytes from normal BDF~ mice were activated by concanavalin A (5 ~tg/ml, Pharmacia) or lipopolysaccharide (E. coli 055:B5, 20 ~tg/ml, Sigma) in plastic 25 cm 2 Linbro flasks (10 ml) for 24 h. T and B lymphocytes preactivated with concanavalin A and lipopolysaccharide, respectively, were isolated by positive penning [3]. Immunofluorescent staining of [3] showed the purity of isolated T and B lymphocytes to be almost 100%.For preparing culture supernatants, preactivated lymphocytes (3-4• were cultured in 24-well plates (Linbro) for 24 h. Then the supernatant was purified from ceils by centrifugation and stored at -20oC.In the cytostatic test, BMC (3xl05/well) were cultured with or without the supernatant (25%) from preactivated T or B lymphocytes in round-bottom 96-well plates (BDSL) for 20 h. After the medium 0007-4888/98/0006-0585520.00 9Kluwer Academic/Plenum Publishers