Analysis of the limiting-dilution assay used for estimating frequencies of immunocompetent units

Discovery of Novel N-(Anthracen-9-ylmethyl) Benzamide Derivatives as ZNF207 Inhibitors Promising in Treating Glioma

Targeting tumor stemness is an innovative approach to cancer treatment. Zinc Finger Protein 207 (ZNF207) is a promising target for weakening the stemness of glioma cells. Here, a series of novel N-(anthracen-9-ylmethyl) benzamide derivatives against ZNF207 were rationally designed and synthesized. The inhibitory activity was evaluated, and their structure-activity relationships were summarized. Among them, C16 exhibited the most potent inhibitory activity, as evidenced by its IC50 values ranging from 0.5-2.5 μM for inhibiting sphere formation and 0.5-15 μM for cytotoxicity. Furthermore, we found that C16 could hinder tumorigenesis and migration and promote apoptosis in vitro. These effects were attributed to the downregulation of stem-related genes. The in vivo evaluation demonstrated that C16 exhibited efficient permeability across the blood-brain barrier and potent efficacy in both subcutaneous and orthotopic glioma tumor models. Hence, C16 may serve as a potential lead compound targeting ZNF207 and has promising therapeutic potential for glioma.

Analysis of cellular interactions in limiting dilution cultures

Limiting dilution (LD) cultures are often used to study cellular heterogeneity in responses of murine splenocytes to specific or polyclonal activation. LD titration curves often reveal a nonlinear dependence of response on input cell dose. Although 'zigzag' shaped curves of this kind are often interpreted and analyzed as resulting from interactions among three distinct cell types, we observe that a more parsimonious two cell model, including a cell type that can generate both positive and negative effects, provides better fit to a wide range of experimental data. We have developed mathematical models for the accurate estimation of the frequencies of both interacting cell types and of the parameters for their multi-hit interaction. We show examples of LD cultures in which specific experimental manipulations alter the frequency of only one of the two cell types, or alter the interaction parameters without a change in responder frequency. We also provide a simplified method for approximation of the model parameters using graphical approaches and simple algebra. Lastly, we present an improved method for calculation of the effect generated per responder cell in microclonal cultures.

Limiting dilution assays for the determination of immunocompetent cell frequencies. III. Validity tests for the single-hit Poisson model

A statistical method was developed to test the validity of the single-hit Poisson model in limiting dilution assays used to determine immunocompetent cell frequencies. Principles of bioassay, validity tests, and the distinction between model-discrimination experiments and parameter-estimation assays are reviewed in the Introduction. The new test derived and then demonstrated with previously published data is intended to be used for parameter-estimation assays based upon the single-hit Poisson model. It is a family of related chi 2, t, and F tests for deviations from zero of the slopes of weighted least squares regression plots. These plots regress the logarithms of single-dose estimates fi of the frequency phi on the total cell doses lambda i and fi on the total cell dose reciprocals 1/lambda i, that is, Yi = ln fi on Xi = lambda i and Yi = fi on Xi = 1/lambda i. The test discriminates against alternative models with multiple-hit/target response-generation processes, a variable number (dose-dependent) of false negatives, and a constant number (dose-independent) of false positives. Its purpose as a test for parameter-estimation assays, though, is to detect deviations from the single-hit Poisson model and not to select one of these alternative models. Tests for model-discrimination experiments to select or 'prove' an unknown alternative model are considered in light of relevant literature reviewed in the Discussion.

Frequencies of Epstein-Barr virus-inducible IgM anti-IgG B lymphocytes in normal children and children with juvenile rheumatoid arthritis

The relative frequencies of IgM antiIgG autoantibody (rheumatoid factor) producing cells induced by the polyclonal B cell activator Epstein-Barr virus were measured in peripheral blood lymphocyte cultures of normal children and patients with juvenile rheumatoid arthritis. The frequencies of rheumatoid factor precursor B cells in normal children were lower than adults, but higher than neonates. The frequency increased with the age of the donor. In seronegative children with the systemic-onset or pauciarticular-onset types of juvenile rheumatoid arthritis, the number of IgM antiIgG inducible B cells was not significantly different (P greater than 0.05) from age-matched controls. Patients with seropositive juvenile rheumatoid arthritis or seropositive adult rheumatoid arthritis had significantly higher IgM antiIgG precursor cell frequencies than age-matched normal subjects (P less than 0.01 and P less than 0.02, respectively). In contrast, the patients with seronegative polyarticular-onset juvenile rheumatoid arthritis had an average precursor frequency significantly lower than normal age-matched controls (P less than 0.05), analogous to results previously noted in adult seronegative rheumatoid arthritis. Thus, both children and adults with seronegative polyarticular rheumatoid arthritis had a deficiency in B cells that produce IgM antiIgG and that are induced by Epstein-Barr virus. This distinguished them from seropositive juvenile rheumatoid arthritis and rheumatoid arthritis patients, normal subjects, and patients with the pauciarticular-onset and systemic-onset types of seronegative juvenile rheumatoid arthritis.

Role of the ABO, Secretor, and Lewis determinants in the primed lymphocyte test

The antigenic determinants of the combined ABO, Lewis, and Secretor genes have been detected on the surface of lymphocytes by the lymphocytotoxicity test. We have studied the role of these determinants in the primed lymphocyte test (PLT), and the data demonstrate that Lewis incompatibility causes proliferative responses in PLT. On the other hand, no effects of ABO and Secretor incompatibilities were observed in this test. The frequency of the alloantigen-reactive cells (ARC) responding to Lewis and HLA-DR antigens in PLT was estimated by the limiting dilution analysis. The frequency of ARC to allogeneic Lewis-negative donors, who are positive for the sensitizing HLA-DR antigens ranged between 1:58 and 1:97. The incidence of ARC to Lewis-positive allogeneic donors who did not carry the sensitizing HLA-DR specificity was 1:94 to 1:142. These results demonstrate the presence of lymphocyte clones that are able to respond to antigens of the Lewis system. This study suggests that non-HLA antigens belonging to the Lewis system can cause stimulation of lymphocytes in the PLT test.

Limiting dilution analysis of alloantigen-reactive cells which respond to allogeneic lymphocytes in human MLC and PLT

We have determined the frequency of the alloantigen-reactive cells (ARC) in human MLC and PLT by the limiting dilution analysis. In PLT, the frequency of the ARC to the original sensitizing donor ranged between 1:32 to 1:62, an increase of six to nine-fold after priming in MLC. The MLC primed populations were also enriched (three to five fold) for the ARC responding to the PL-positive allogeneic donors. The incidence of the ARC was 1:62 to 1:118 with donors positive for the sensitizing HLA-DRw antigen and 1:77 to 1:144 with donors negative for the specific HLA-DRw determinant. The results from experiments utilizing pooled stimulating cells from the original and allogeneic donors suggest that same subpopulation of cells responds to the sensitizing HLA-DRw determinant, whether it is presented by the specific stimulator or by a third-party allogeneic donor. On the other hand, different subpopulations of alloreactive cells respond to different alloantigens. In MLC experiments between HLA-identical siblings, the incidence of the ARC ranged between 1:995 to 1:1673. The responses of the ARC to non-HLA antigens were observed under conditions where responder cells were limiting. Also, the responses of the limiting numbers of responding cells were inhibited by mitomycin-treated autologous lymphocytes. Nonresponse in MLC combinations with higher responder cell numbers was not due to small numbers of stimulating cells.

Quantitative studies of alloantigen-reactive human lymphocytes in primary and secondary MLC

The number of alloantigen-reactive cells in human peripheral blood was estimated by a limiting dilution analysis. In MLC combinations between allogeneic unrelated donors, the frequency of alloantigen-reactive cells ranged between 1:241 to 1:486. The frequency of alloantigen-reactive cells to the specific donor was increased six- to eight-fold after priming in MLC. The results demonstrate that specific "memory" cells are enriched in long-term MLC. In limiting dilution experiments between HLA-identical siblings, the frequency of alloantigen-reactive cells ranged from 1:1160 to 1:1740. The data point to the existence of a lymphocyte-defined antigen system controlled by a genetic region that is not linked to HLA. The results suggest that the lymphocyte clones that are able to react to non-HLA antigens probably consist of a small number of lymphocytes. Finally, the response of these clones of cells to non-HLA antigens was observed only under conditions where responder cells were limiting.

Quantification of antigen-reactive cells among human T lymphocytes

The number of antigen-reactive cells among human peripheral blood T lymphocytes was estimated by a limiting dilution analysis. Antigen-induced lymphocyte activation was measured by means of incorporation of tritiated thymidine [3H]dThd. We have studied the frequency of memory T cells for the bacterial antigens tuberculin PPD and tetanus toxoid in immune donors, as well as the frequency of alloantigen-reactive T cells. In 11 different donors, the observed frequencies of the antigen-reactive T cell ranged between 1:300 and 1:16 000 for PPD; for tetanus toxoid values, between 1:750 and 1:11 500 were obtained in 5 different donors. The frequency of alloantigen-reactive T cells was found to be higher: between 1:200 and 1:600 (n = 10). For 3 donors, the estimated frequencies proved to be reproducible over a period of several months. Finally, a correlation could be demonstrated between the frequency of PPD-reactive T cells and the [3H]dThd incorporation of 4 X 10(4) PPD-stimulated lymphocytes.