Early detection and specificity analysis of human cytolytic T lymphocyte (CTL) colonies generated in soft agarose culture: a potential assay for definition of CTL defined (CD) determinants

In this communication we describe and early, large-scale screening assay for the detection of colonies with varied cytolytic specificity. The colonies are generated in soft agarose culture from day 3 mixed lymphocyte culture (MLC) alloactivated cells. A cell mediated lympholysis (CML) assay utilizing as few as 500 target cells has made it possible to prescreen for cytolytic T lymphocyte (CTL) colonies and to test for antigen specificities as early as 11 and 14 days, respectively, after MLC priming. Large numbers of colonies, from 80 to over 150, have been prescreened against a specific sensitizing target cell, and as many as 30 CTL colonies have been simultaneously tested against a panel of multiple targets carrying defined HLA-A, -B, -C, -DR antigens to evaluate antigen specificity. All CTL colonies are lytic against the specific sensitizing target cell and do not lyse the target autologous to the responder. Some are found to be operationally specific in that they lyse only those target cells which share HLA serologically defined (SD) antigens with the sensitizing cells, and other show cytolytic patterns which are not correlated with known HLA-SD antigens. These observations support, at a much finer level of analysis, the possible distinction between SD and CTL defined (CD) determinants.

Helper cells in murine thymus for the generation of primary cytolytic T lymphocyte (CTL) responses in vitro

Thymocytes used as responding cells in a mixed leukocyte culture with gamma-irradiated splenic stimulating cells generated highly significant proliferative and cytolytic responses when responding and stimulating cells differed by the entire H-2 complex or at H-2K plus H-21 regions. On the other hand, when the difference was only an H-2K region, very little, if any, proliferative response was detectable and no cytolytic response was found. Because it has been claimed by others that thymocytes do not include cells needed to provide the help required for the generation of a cytolytic response and yet we have found a highly significant response in thymocytes, we have analyzed, in 2 systems, the possible role of back-response by stimulating spleen cells in the generation of cytolytic activity by responding thymocytes. In the first system, spleen cells were depleted of T lymphocytes by treatment with anti-Thy-1.2 antiserum plus complement. In the second system, F1 hybrid mouse spleen cells were used to stimulate parental responding thymocytes. In both cases, no back-response as measured by cell proliferation in mixed leukocyte culture was detected, while both types of spleen cells still stimulate significant cell proliferation and cytolytic activity from responding thymocytes, as well as from responding spleen cells. Furthermore, it was found that in the presence of stimulating spleen cells (either T lymphocyte-depleted or not) that differ from the responding thymocytes at the entire H-2 complex, thymocytes were capable of generating a significant and specific cytolytic response to H-2K region different stimulating spleen cells (either T lymphocyte-depleted or not). These results are compatible with the suggestion that there are sufficient numbers of helper cells in the unfractionated thymocyte population for the generation of primary cytolytic T lymphocyte responses in vitro.

Helper cells in murine thymus for the generation of primary cytolytic T lymphocyte (CTL) responses in vitro

Thymocytes used as responding cells in a mixed leukocyte culture with gamma-irradiated splenic stimulating cells generated highly significant proliferative and cytolytic responses when responding and stimulating cells differed by the entire H-2 complex or at H-2K plus H-21 regions. On the other hand, when the difference was only an H-2K region, very little, if any, proliferative response was detectable and no cytolytic response was found. Because it has been claimed by others that thymocytes do not include cells needed to provide the help required for the generation of a cytolytic response and yet we have found a highly significant response in thymocytes, we have analyzed, in 2 systems, the possible role of back-response by stimulating spleen cells in the generation of cytolytic activity by responding thymocytes. In the first system, spleen cells were depleted of T lymphocytes by treatment with anti-Thy-1.2 antiserum plus complement. In the second system, F1 hybrid mouse spleen cells were used to stimulate parental responding thymocytes. In both cases, no back-response as measured by cell proliferation in mixed leukocyte culture was detected, while both types of spleen cells still stimulate significant cell proliferation and cytolytic activity from responding thymocytes, as well as from responding spleen cells. Furthermore, it was found that in the presence of stimulating spleen cells (either T lymphocyte-depleted or not) that differ from the responding thymocytes at the entire H-2 complex, thymocytes were capable of generating a significant and specific cytolytic response to H-2K region different stimulating spleen cells (either T lymphocyte-depleted or not). These results are compatible with the suggestion that there are sufficient numbers of helper cells in the unfractionated thymocyte population for the generation of primary cytolytic T lymphocyte responses in vitro.

Differential allo-response of murine thymocytes to H- 2 K region different recombinants and to H-2Kb mutants

Thymocytes used as responding cells in a mixed leukocyte culture with x-irradiated splenic stimulating cells generate highly significant proliferative and cytotoxic responses when responding and stimulating cells differ by the entire H-2 complex. On the other hand, when the genetic difference between responding and stimulating cells is only a K region, very little, if any, proliferative response is detectable and no cytotoxic response is found. In contrast, when responding and stimulating cell donors differ by a spontaneous mutation in the K region of the H-2 complex, as found in B6.C-H-2ba, B6-H-2bd and B6.C-H-2bf, highly significant proliferative and cytotoxic responses can be obtained. These results, thus, argue that the H-2 mutants cannot, with regard to their relationship to the parental strain, be readily equated with a K region difference as defined in the recombinant inbred strains.

Differential allo-response of murine thymocytes to H- 2 K region different recombinants and to H-2Kb mutants

Thymocytes used as responding cells in a mixed leukocyte culture with x-irradiated splenic stimulating cells generate highly significant proliferative and cytotoxic responses when responding and stimulating cells differ by the entire H-2 complex. On the other hand, when the genetic difference between responding and stimulating cells is only a K region, very little, if any, proliferative response is detectable and no cytotoxic response is found. In contrast, when responding and stimulating cell donors differ by a spontaneous mutation in the K region of the H-2 complex, as found in B6.C-H-2ba, B6-H-2bd and B6.C-H-2bf, highly significant proliferative and cytotoxic responses can be obtained. These results, thus, argue that the H-2 mutants cannot, with regard to their relationship to the parental strain, be readily equated with a K region difference as defined in the recombinant inbred strains.

Cell-mediated immunity: differential maturation of mixed leukocyte reaction and cell-mediated lympholysis

While spleen cells from neonatal B10 (H-2b) are reactive (proliferate) in one-way mixed leukocyte culture, cell-mediated lympholysis reactivity does not arise until 7 days of age. When B10 cells are sensitized to B10.D2 (H-2d), cross-killing of third-party B10.BR (H-2k) target is always lower than the specific killing of B10.D2 targets and is not demonstrable until 27 days after birth.

Stress: a factor to be considered in heterotrophic microorganism enumeration from aquatic environments

Heterotrophic microorganisms in water samples are susceptible to the transient stress of warmed agar used in the standard methods pour plate procedure, causing significantly decreased recoveries in comparison with a spread plate technique. Microbial starvation can increase susceptibility to a transient warming stress. The standard plate count procedure, as presently described, should not be considered for quantitation of microorganisms from aquatic environments.