Use of a P815-derived line with an amplified adenosine deaminase gene: an improved target for cellular cytotoxicity

Ontogeny of adenosine deaminase in developing trophoblast and decidual cells of rat and hamster

The enzyme adenosine deaminase (ADA) is expressed at high level in the tissue of foeto-maternal interface during early pregnancy. As the main constituents of this interface are trophoblast (TR) and decidual cells (DC), the enzyme was estimated in isolated TR and DC to determine the extent of contribution by the respective cells. The enzyme level was estimated in cytosolic fraction, cell lysate and in conditioned media of these cells in rat and hamster. In both species the concentration of ADA was found to be markedly high in cytosolic fraction over to the cell lysate and the conditioned media in both TR and DC. Species-wise, it was higher in hamster. Cell-wise, the enzyme activity was significantly higher in TR than DC in rat but equal in hamster. In the conditioned medium, also, the enzyme activity was higher in TR in both species. The inference drawn from the results are: 1) the maximum enzyme activity in cytosolic fraction of TR and DC of both species clearly indicates equal involvement of the cells that constitute foeto-maternal unit, 2) the enhanced level of enzyme in TR and DC of hamster over to those of rat is possibly due to the higher proliferative activity in the cells of this species because of shorter gestation (16-17 days in hamster and 22-23 days in rats).

Fluorescent europium chelates as target cell markers in the assessment of natural killer cell cytotoxicity

A time-resolved fluorometric assay for the detection of natural killer cell activity against target cells labelled with the fluorescent chelate europium-6,6"-bis[N,N-bis(carboxymethyl)-aminomethyl]-4'-phenyl-2,2',6', 2"-terpyridine (EuCAPT) has been developed. In the assay released EuCAPT from lysed K-562 cells is measured in the supernatant after co-incubation of the target cells with effector cells. Thus, the performance of the assay is essentially similar to the previously described EuDTPA assay and the widely used 51Cr assay. EuCAPT is released from target cells lysed by effector cells faster than 51CrO4(2-) but somewhat slower than EuDTPA. In contrast to methods based on prompt fluorometry the autofluorescence from culture medium supplemented with serum can be avoided by the use of time-resolved fluorometry. The result shows that fluorescent europium chelates provide an alternative to radioactive markers currently used for the assessment of in vitro cellular cytotoxicity.

Determination of cytotoxic T lymphocyte activity by time-resolved fluorometry using europium-labelled concanavalin A-stimulated cells as targets

Time-resolved fluorometry was used to detect the cytolysis of concanavalin A-stimulated blast cells by employing cells stimulated in a mixed lymphocyte culture as effectors. The target cells were labelled with europium diethylenetriaminopentaacetate (EuDTPA) chelates. The results obtained showed that this method, which has been successfully applied to the measurement of natural killer cell activity, was also applicable to the more specific cytotoxic T lymphocyte reaction. The specific release was higher with EuDTPA-labelled target cells than with 51chromium-labelled target cells. As with 51chromium, EuDTPA can be used to distinguish between the cytolysis of specific and non-specific target cells.

T cell-mediated hepatitis in mice infected with lymphocytic choriomeningitis virus. Liver cell destruction by H-2 class I-restricted virus-specific cytotoxic T cells as a physiological correlate of the 51Cr-release assay?

A model for immunologically T cell-mediated hepatitis was established in mice infected with lymphocytic choriomeningitis virus (LCMV). The severity of hepatitis was monitored histologically and by determination of changes in serum levels of the enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutamate dehydrogenase (GLDH), and alkaline phosphatase (AP). Kinetics of histological disease manifestations, increases of liver enzyme levels in the serum, and cytotoxic T cell activities in livers and spleens all correlated and were dependent upon several parameters: LCMV-isolate; LCMV-WE caused extensive hepatitis, LCMV-Armstrong virtually none. Virus dose. Route of infection; i.v. or i.p. infection caused hepatitis, whereas infection into the footpad did not. The general genetic background of the murine host; of the strains tested, Swiss mice and A-strain mice were more susceptible than C57BL or CBA mice; BALB/c and DBA/2 mice were least susceptible. The degree of immunocompetence of the murine host; T cell deficient nu/nu mice never developed hepatitis, whereas nu/+ or +/+ mice always did. B cell-depleted anti-IgM-treated mice developed immune-mediated hepatitis comparably or even more extensively than control mice. Local cytotoxic T cell activity; mononuclear cells isolated from livers during the period of overt hepatitis were two to five times more active than equal numbers of spleen cells. Adoptive transfer of nylon wool-nonadherent anti-Thy-1.2 and anti-Lyt-2 plus C-sensitive, anti-L3T4 plus C-resistant lymphocytes into irradiated mice preinfected with LCMV-WE caused a rapid time- and dose-dependent linear increase of serum enzyme levels. This increase was caused by adoptive transfer of lymphocytes if immune cell donors and recipient mice shared class I, but not when they shared class II histocompatibility antigens. The donor cell dose-dependent increase of these enzymes was first measurable 6-18 h after transfer with 2 X 10(8) cells or 3 X 10(6) cells, respectively. The time-dependent increase caused by the adoptive transfer of 1-2 X 10(8) cells was strictly linear during a period of up to 25-40 h. These results indicate single-hit kinetics of liver cell death and suggest that effector T cells destroy infected liver cells via direct contact rather than via soluble toxic mediators. The results may represent the best in vivo correlate of the in vitro 51Cr-release assay that has been analyzed so far, and strongly support the view that antiviral cytotoxic T cells are directly cytolytic in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Azacytidine-induced reactivation of adenosine deaminase in a murine cytotoxic T cell line

In C57BL/6 mice, cytotoxic T lymphocyte (CTL) lines have previously been found to exhibit low (less than 150 U/mg) or undetectable (less than 20 U/mg) adenosine deaminase (ADA) levels (Minkowski, Castellazzi and Buttin, J. Immunol. 1984. 133: 52) in contrast to what has been seen in T helper lines (1770 +/- 340 U/mg; Minkowski and Bandeira, Cell. Immunol. 1985. 95: 380). Treatment of one of these CTL ADA- lines with the demethylating agent 5-azacytidine gave rise to an ADA+ population. Subsequent cloning allowed the recovery of pure ADA+ clones showing a rather narrow range of activity with an average value of 2030 +/- 504 U/mg. The restored ADA+ activity is stable over several months of continuous growth. It is identical to the activity of C57BL/6 thymic cells or C57BL/6 T tumor lines regarding its sensitivity to ADA inhibitors 2-deoxycoformycin and erythro-9-(2-hydroxyl-3-nonyl)adenine, and its electrophoretic mobility under nondenaturing conditions (starch gel and isoelectric focusing). An ADA-specific, 1.4-kb mRNA is present in the reactivated clones but is undetectable in the CTL ADA- parental line. These results demonstrate that the ADA- phenotype is due to an extinction of the corresponding gene. They suggest that the extinction of the ADA gene which appears to be specific for CTL and to take place in vivo during T cell differentiation may result from increased methylation in or near the ADA gene. This extinction seems to affect specifically ADA since nucleoside phosphorylase, the enzyme which follows ADA in the purine salvage pathway, is present at equivalent levels in the ADA- and ADA+ CTL clones.