title: Enhancement of weak mixed lymphocyte-type reactions by hydrophilic polymers.
abstract: Two hydrophilic polymers, dextran and polyethylene glycol, were found to enhance in vitro MLR-type reactions which are weak or nonexistent in normal culture media. BALB/c and C57BL/6 thymocytes were cultured for 4 days in Eagle's MEM + 10% FCS, with or without the x-irradiated lymphomas LSTRA AND EL-4, respectively. By thymidine incorporation no stimulation was observed with EL-4 in plain culture whereas occasionally a very small stimulation was observed with LSTRA. Four percent dextran (w/v, m.w. greater than or equal to 40,000) improves stimulation (E/C) by about 2-fold. The effect of polyethyleneglycol m.w. 6,000 (PEG-6) is much more pronounced. At the optimal concentration of 4 to 5%, PEG-6 causes an increase of 5- to 20-fold in the stimulation index. The PEG-6 effect can also be observed microscopically by the appearance of numerous blasts clustered around the tumour cells. PEG-6 by itself has little effect on  thymocytes in the absence of tumor cells. In the case of one-way allogeneic MLR under suboptimal ratios, dextrans (m.w. greater than or equal to 40,000) enhance the reaction dramatically. We speculate that these effects are occurring via a change in the solvent (such as solvent exclusion) in a way which enhances immunologic interactions under conditions which are tolerable to cells in vitro.
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic; D003911:Dextrans / Q000494:pharmacology; D004306:Dose-Response Relationship, Immunologic; D000939:Epitopes; D007959:Lymphocyte Culture Test, Mixed; D008214:Lymphocytes / Q000166:cytology / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009374:Neoplasms, Experimental / Q000276:immunology; D011092:Polyethylene Glycols / Q000494:pharmacology; D011108:Polymers / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D003911:Dextrans; D000939:Epitopes; D011108:Polymers; D011092:Polyethylene Glycols