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Small B-cell lymphocytic lymphoma/chronic lymphocytic leukemia, which typically affects elderly people, is a group of conditions that are not clinically uniform. It has been suggested that using the combined activity of the monoclonal antibody anti-CD20 (rituximab) and Listeria monocytogenestoxin listeriolysin O (LLO) for this condition could produce an enhanced treatment effect. Here, we tested the effect of the joint activity of rituximab and LLO, which is a cell membrane toxin, in human leukemia cell lines. The human B-leukemia Raji cell line, which expresses CD20, and the T-cell Jurkat cell line, which does not express CD20, for comparison were used in model tests. Cell cytotoxicity of rituximab or LLO and both applied jointly to the cell lines was compared in the presence of human plasma complement. Optimal cytotoxic effects dependent on rituximab or LLO concentration were tested separately. LD50values were determined and used for optimal application of a mixture of the two factors. The cytotoxic effect on Raji cells of both rituximab and LLO was more than 2.5 times that of LLO alone and 1.5 times that of rituximab alone. At the highest tested concentrations, a mixture of the tested factors had a non-specific cytotoxic effect on the Jurkat cell line, as well. The rituximab and LLO binding sites appear to be in a similar region of the Raji leukemia cell membrane, suggesting an effective interaction of both factors. The joint interaction of these compounds in cell membrane pore formation suggests an explanation for the more effective cytotoxic activity that their combination was observed in this experiment.

The purpose of the observations was the viability and quality evaluation of E. coli bacteria encapsulated in hollow fiber membranes (HF) in short in vivo and in vitro experiments. A polypropylene, surface-modified hollow fiber was applied for immunoisolation of E. coli bacteria transfected with a green fluorescent protein (E. coli GFPI). The presence of GFP fluorescence of organisms was assessed with the use of flow cytometry. The E. coli GFPIs were then observed for the period of 5 days in in vitro experiments in the culture medium. A single IPTG (isopropyl β-D-1-thiogalactopyranoside) induction of GFP gene appeared to be adequate for an expression of GFP protein for 5 days. The GFP expression values observed for E. coli GFPs encapsulated in HF during culture in different culture media were comparable. The survival of E. coli GFPIs encapsulated in HF after 1, 2, 4, or 5 days of subcutaneous implantation into mice was evaluated. The explanted E. coli GFPIs exhibited mean expression 603 ± 17 (n = 32) units of fluorescence during the implantation period. The values obtained were comparable for selected days of observation. It was observed that the membranes applied ensured the bacteria growth within the HF's space only.

Mouse lymphatic leukemia L1210 cells were characterized with polyclonal and monoclonal antibodies and lectins. The cells were found to have the phenotype IgG-, Thy-1.2-, Lyt-1-, Lyt-2-, asialo-GM-, TL-, I-Ad-, IL-2R+, peanut agglutinin+, and Helix pomatia lectin +/-. They retained expression of H-2Kd and H-2Dd. Thus, these cells resemble "null" cells.

CD2F1 mice were immunized against semisyngeneic L 1210 leukemia. Immunization was achieved by four i.p. injections, in weekly intervals, of L 1210 cells treated in vivo twice with 200 mg/kg of cyclophosphamide. The immunized animals survived i.p. challenge with 1000 untreated L 1210 cells that was lethal for nonimmunized mice. The immunity could be abrogated in vivo with anti-mouse thymocyte serum, carrageenan or reserpine, but not by anti-mouse IgG serum, suggesting participation of T lymphocytes and macrophages in the response. Moreover, lymphocytes and macrophages from the peritoneal cavity of immunized mice were cytotoxic in vitro for L 1210 cells. The immunity, at least partially, could be adoptively transferred with peritoneal exudate cells or splenocytes.

Of a number of factors involved in apoptosis, protease activity may play a crucial role. We show that N-benzyloxycarbonyl-Ile-Glu(O-t-butyl)-Ala-leucinal (PSI), a selective inhibitor of the chymotrypsin-like activity of the proteasome, induces massive apoptosis in murine leukaemia L1210 cells. At 50 nM concentration, PSI induces a block of cytokinesis, while higher concentrations (500 nM) cause S phase block and massive apoptosis. Z-Leu-leucinal, a specific calpain inhibitor, did not induce apoptosis. In contrast to previous reports, TNF-α did not enhance apoptosis when combined with PSI. Our results suggest that proteasome inhibitors may be considered as potential anti-neoplastic agents.

Auto- and allogeneic chondrocytes isolated from septal cartilage by enzymic digestion were transplanted into rabbits together with intact fragments of the same cartilage. In other animals fragments only of cartilage were grafted. Cartilage formed by autogeneic chondrocytes was devoid of infiltration, whereas that formed by allogeneic chondrocytes was mostly surrounded by massive infiltration, composed predominantly of lymphocytes and plasma cells. Resorption of such cartilage was also found. Auto- and allogeneic fragments transplanted alone did not evoke infiltrations. When similar fragments were transplanted together with isolated chondrocytes, infiltrations were frequently formed in the vicinity of the allogeneic fragment. It is concluded that isolated allogeneic chondrocytes evoke immunization and may perhaps sensitize the animals against allogeneic fragments of cartilage.

Chondrocytes isolated from the nasal septal cartilage of almost mature female rabbits by the joint action of trypsin and collagenase were injected into muscles of male rabbits. Cartilage formed after transplantation of chondrocytes contained a high percentage of cell nuclei with characteristic sex chromatin; it was morphologically similar to septal cartilage. In older transplants slight resorption of cartilage was observed.