Macrophages overcome mycoplasma infections of cells in vitro.

Mycoplasmal infections still cause severe problems in cell cultures, particularly permanent lines, and although rapid detection is possible the only methods proposed for the elimination of the mycoplasma are either laborious or unsatisfactory. Treatment with antibiotics often leads to the development of resistance and we have found it more successful to passage contaminated cells in nude (thymusless) mice although the cells cannot always be recovered. But when the resulting subcutanous tumours can be collected, the cells are both free of mycoplasma and accompanied by a large number of macrophages. Because nude mice have no T cell-dependent immune response, it seemed possible that the macrophages could be responsible for the elimination of the mycoplasma. The experiments reported here support this hypothesis, and have led to a rapid and reproducible technique for eliminating mycoplasma in vitro by a brief co-cultivation of contaminated cells with mouse macrophages, in the presence of antibiotics.

Adherent cells as targets in mitogenic T-lymphocyte stimulation: replacement of lymphocyte-bound mitogens by nonmitogenic substances.

The sequence of events in mitogenic T-lymphocyte activation was investigated by employing purified mouse peritoneal adherent cells and T-lymphocyte populations. After treatment of adherent cells with the oxidizing agents sodium periodate or neuroaminidase plus galactose oxidase and removal of the mitogens, the cells acquired the ability to stimulate purified T-lymphocytes added subsequently. For this process of T-lymphocyte activation, the additional presence of the membrane interacting substances polyethylene glycol, dextran, nonmitogenic Helix pomatia agglutinin, or inactivated sendai virus was required. Lysates of mitogen-treated peritoneal adherent cells were able to replace the adherent cells in the cultures.

Cooperative pathway induction of T lymphocyte mitogen stimulation.

Isolated peritoneal mouse macrophages pretreated with the mitogenic enzyme combination neuraminidase (EC 3.2.1.18) plus galactose oxidase (EC 1.1.3.9.) (NAGO), or with NaIO4, stimulate macrophage-depleted lymphocytes mitogenically by a macrophage-derived signal, different from the originally used mitogen. Polyethylene glycol (PEG) treatment of the cultures, although itself nonmitogenic, strongly enhances the mitogenic response of the lymphocytes. Under culture conditions the macrophage-derived signal is transmitted to lymphocytes by direct cell contact, a finding which explains the need of a critical cell density for T lymphocyte stimulation. In the absence of macrophages, lysates from mitogen-preteated macrophages stimulate column-purified lymphocytes in the presence of PEG. Our results indicate that mitogenic activation of lymphocytes is mediated through two sequential triggering events, induction (by mitogen treatment) of a macrophage-derived signal and commitment (by nonmitogenic PEG treatment) of lymphocytes to react to the signal. Reconstitution of the mitogenic response can be achieved by a sequential induction of both these events.

Preformed poly(A)-containing RNA in zoospores of Blastocladiella emersonii.

Discharged zoospores of Blastocladiella emersonii contain poly(A)-containing RNA, which is performed during the initial stages of zoospore differentiation in the sporangium and is stable in vivo for at least 4 h. The average molecular weight of this RNA fraction is estimation to be 5.5-10(5) or 1600 nucleotides. The average length of the poly(A) sequence is approx. 100 nucleotides Poly(A)-containing RNA does not appear to accumulate in a gamma-particle fraction previously suggested to be involved in the storage of mRNA.