Antibody-dependent cell-mediated cytotoxicity: a flow cytometry-based assay using fluorophores.

Using flow cytometry (FCM), an assay has been developed for the determination of antibody-dependent cell-mediated cytotoxicity (ADCC). Target cells were labelled with a membrane dye, PKH-26, to allow discrimination when incubated with effector cells and antibody. Post-incubation, cell death within the PKH-26+ target cell population was assessed by the addition of the viability probe TO-PRO-3 iodide (TP3). This ADCC method allows analysis to be conducted on a single cell basis and overcomes the need for radiochemicals. This communication indicates that the assay is accurate and reproducible with the potential to be a useful tool for evaluating the therapeutic potential of antibodies and antibody-based reagents.

Development of a novel flow cytometric cell-mediated cytotoxicity assay using the fluorophores PKH-26 and TO-PRO-3 iodide.

A flow cytometric (FCM) assay has been developed for the determination of cell-mediated cytotoxicity (CMC). In the assay, the target tumour cell population was labelled with a membrane dye, PKH-26, prior to incubation with splenocyte effector cells. Cell death within the target population was assessed by the addition of the viability probe TO-PRO-3 iodide (TP3) and analysed by flow cytometry. The extent of cytotoxicity was determined by the relative number of live target cells labelled with PKH-26 only and dead, permeabilised cells labelled with both PKH-26 and TP3. This CMC method allows the analysis to be conducted on a single cell basis and overcomes the need for radiochemicals. This communication indicates that the FCM assay is an accurate and reproducible experimental system capable of analysing natural killer (NK) cell and antibody-dependent cell-mediated cytotoxicity. The procedure is comparable to the chromium release assay. We believe that this is one of the first demonstrations of an FCM-based antibody-dependent cell-mediated cytotoxicity (ADCC) assay.

A transgenic mouse model for tumour immunotherapy: induction of an anti-idiotype response to human MUC1.

MUC1 is a membrane bound, polymorphic epithelial mucin expressed at the luminal surface of glandular epithelium. It is highly expressed in an underglycosylated form on carcinomas and metastatic lesions and is, therefore, a potential target for immunotherapy of cancer. The monoclonal antibody HMFG1 binds the linear core protein sequence, PDTR, contained within the immunodominant domain of the tandem repeat of MUC1. The efficacy of murine and humanized HMFG1 (Ab1) used as an anti-idiotypic vaccine was examined in mice transgenic for human MUC1 (MUC1.Tg) challenged with murine epithelial tumour cells transfected with human MUC1. Humoral idiotypic cascade through Ab2 and Ab3 antibodies was observed in MUC1.Tg mice following multiple antibody inoculations in the presence of adjuvant. Impaired tumour growth at day 35 and highest Ab3 levels were found in mice that had received mHMFG1 with RAS adjuvant. However, comparison of Ab3 levels in individual mice with tumour size in all treatment groups did not show a correlation between smaller tumours and increased levels of anti-idiotype antibody. This suggests that the anti-tumour effects of anti-idiotype vaccination are not solely related to the induction of idiotypic antibody cascades and probably involve other mechanisms.