Cytotoxic Reactivity of Human Lymphocytes Cultured in Vitro

Recent evidence indicates that both natural killer and killer cells active in antibody-dependent cell-mediated cytotoxicity are cell types that bear Fc receptors. Natural killer and antibody-dependent cell-mediated cytotoxicity have also been shown to be in a SRBC-rosetting subpopulation. Human mononuclear peripheral blood leukocytes were cultured under various conditions to examine natural killing and antibody-dependent cell-mediated cytotoxicity. It was of interest to determine if these activities would be maintained or augmented under various culture conditions. Before culture, normal mononuclear peripheral blood leukocytes were tested in a 4-hr 51Cr release assay against K-562 to measure natural killer activity, and against antibody-coated Chang liver cells to measure antibody-dependent cell-mediated cytotoxicity. Fc receptor-bearing cells were removed by adsorption to immobilized antigen-antibody complexes. When lymphocytes were cultured alone, we often observed what we call cytotoxicity from cultured cells (CCC). The amount of cytotoxicity against K-562 and in antibody-dependent cell-mediated cytotoxicity was dependent on the presence of FBS and proportional to its concentration in the cultures. The presence of FCS resulted in high levels of CCC whereas human serum demonstrated low or negligible activities. This CCC was not directed against FBS-associated antigens. These CCC cannot be called NK since their extensive characteristics are not known. As was characteristic on day 0 for natural killing and antibody-dependent cell-mediated cytotoxicity, the cultured effector cells also contained an Fc receptor.

Therefore, the presence of CCC with features of natural killer and killer cell activities and its regeneration in culture indicate that it must be distinguished from specific tumor reactivity or alloreactivity in mixed lymphocyte and mixed lymphocyte-tumor reactions, particularly when tumor cell lines are used as targets.

Cytotoxicity inhibition assay: cryopreservation and standardization: brief communication

The cytotoxicity inhibition assay is an extremely useful tool for examination of the specificity of cell-mediated cytotoxicity. With this demonstration of cryopreservation of the attacker, target, and inhibitor cells, a powerful new tool is available for the standardization of this assay to better examine the specificity of cytotoxicity assays. Not only can cryopreservation be used to standardize the assay within a single laboratory, but also reagents may now be exchanged between laboratories to better understand the differences in cell-mediated cytotoxicity as observed by different investigators.

Direct comparison of three isotopic release microtoxicity assays as measures of cell-mediated immunity to Gross virus-induced lymphomas in rats

Three isotopic release microtoxicity assays--[125I]5-iodo-2'-deoxyuridine release assay (IRA), 51Cr release assay (CRA), and [3H]proline release assay (PRA)--have been utilized to measure cell-mediated immunity to (C58NT)D, a Gross virus-induced lymphoma in rats. These studies were designed so that all three assays were done under physical conditions as comparable as possible between the assays. A considerable difference was noted in the ability of one or another target cell to function well in each assay. The tissue culture line of (C58NT)D proved an excellent target cell in the long-term assays, whereas the ascites line was inadequate in these same long-term assays. The monolayer Gross virus-induced tumor cell line ERTh/G was resistant to lysis in the short-term CRA but functioned well in the long-term assays. The autologous and thymus cell controls utilized in these studies were reasonably neutral baseline controls for the evaluation of both normal and immune activity. Although all three assays were capable of measuring both natural and immune activity in this systemthe PRA appeared more sensitive at 24 hours and the IRA at 48 hours, whereas the CRA activity with these target cells was only useful in the short-term assays.

Standardization of the chromium-51 release, cell-mediated cytotoxicity assay: cryopreservation of mouse effector and target cells

Utilizing controlled cryopreservation techniques, we were able to standardize the 51Cr release cytotoxicity assay and thereby ensured reliable comparisons between results obtained on different days. Optimal conditions for freezing of both effector and target cells were quite similar. Dimethyl sulfoxide (DMSO) at a concentration of 7.5-10.0% was employed as the cryoprotective agent and cells were frozen at the rate of -1 degrees C/minute. The handling procedures for the cells before and after freezing were important. Factors affecting recovery of functional reactivity were related to toxicity of DMSO for the cells, the osmotic stress placed upon the cells as the DMSO was being removed after thawing, the handling temperature of the freshly thawed cells, and the susceptibility of cells to mechanical damage immediately after thawing. The recovery of lymphocytes after freezing was about 70%; the recovery of cytotoxicity was around 85%. Syngeneic cytotoxic reactivity induced by inoculation with the Moloney strain of murine sarcoma virus was cryopreserved, as were allogeneic cytotoxicity and natural cytotoxic reactivity. Multiple tests employing effector cells from the same frozen pool gave reproducible results; the standard error of the mean percent cytotoxicity was less than 1.5%. Cryopreserved target cells gave decreased day-to-day variability in susceptibility to lysis, since the same population of cells could be employed in each assay. These results demonstrated conclusively that we can now have a constant source of effector cells and target cells, which can be used from assay to assay as an internal standard.

Cryopreservation of human lymphocyte function as measured by in vitro assays

Methods are described by which cryopreserved cells can be utilized in a number of in vitro assays. On a per cell basis, nearly total recovery of function can be demonstrated for lymphocyte transformation (mitogens, antigens and MLC) and rosette-forming cells. Excellent recovery of mononuclear cell production of leukocyte migration inhibitory factor was also observed. Highly reproducible activity was recovered on a per lymphocyte basis in lymphocyte cytotoxicity but with a definite decrement in the percentage recovery. Both for longitudinal studies of immune function and for standardization of these assays in one or more laboratories such cryopreserved cells are ofimmense value and should be widely utilized.

In vivo passive sensitization of normal rabbit leukocytes with sera demonstrating homocytotropic antibody activity

Normal rabbit leukocytes were passively sensitized, as determined by <i>in vitro </i>antigen-induced histamine release, by the i.v. administration of homologous sera demonstrating homocytotropic antibody activity. There was a significant correlation between the magnitude of passive sentization and the PCA titers of the donor sera. Those parameters that affected skin sensitization also affected leukocyte sensitization. Maximal leukocyte sensitization was observed 3 days after serum administration and by the 10th day no significant histamine release was demonstrable.