Discussion paper: the use of glutaraldehyde fixation for the study of the immune response to syngeneic tumor antigen

We have been able to demonstrate that glutaraldehyde fixation of tumor cells or tumor cell membrane fragments protect syngeneic mice against the subsequent challenge with viable cells. To date we have not been able to detect any antibody against the tumor cells in animals so immunized. The specificity of the response is not complete, although a major component of the protective effect of glutaraldehyde-treated tumor cells is immunologically specific.

Paroxysmal nocturanal hemoglobinuria and marrow failure treated by infusion of marrow from an identical twin

An 18-year-old white Canadian male patient with paroxysmal nocturnal hemoglobinuria and refractory marrow failure received a marrow infusion from his normal identical twin brother without prior ablation of the patient's marrow by drugs or irradiation. After 2 years of follow-up, the patient is well with no evidence of clinical disease or significant hematological abnormality. The results suggest that normal marrow stem cells can have a selective advantage over the abnormal paroxysmall nocturnal hemoglobinuria clone.

Antibody-dependent cell-mediated cytotoxicity against melanoma cells induced by plasmapheresis

Patients with disseminated melanoma were treated by repeated plasmapheresis using a continuous-flow blood-cell separator, as part of a study to investigate methods of removing factors from tissue fluids which block cell-mediated immunity. Using 51Cr release cytotoxic assays, it was found that plasmapheresis resulted in removal of serum blocking activity. Post-plasmapheresis sera taken from several patients also increased cell-mediated cytotoxicity by induction of antibody-dependent cell-mediated killing. This effect may have resulted from removal or alteration of circulating immune complexes in the serum. It is not known whether cytotoxic activity induced in this way improves the patient's immune response against their tumours. However, the procedure is well tolerated and these preliminary in-vitro results indicate that this form of therapy could act as an adjunct to other forms of treatment of advanced melanoma.

Characterization of mononuclear effector cells in human blood

The effector cells responsible for cytotoxic activity induced by phytohaemagglutinin, (PHA) pokeweed mitogen (PWM) target cells complexes with IgG antibody has been investigated using cell separation techniques based on rosette formation and separation through Hypaque-Ficoll mixtures. It was shown the PHA-induced cytotoxicity is predominantly a function of T cells and that Fc receptor-bearing cells are not involved to any major extent. Antibody-dependent killing is conversely a function of Fc receptor-bearing cells among which two subtypes can be distinguished. One of these has receptors for activated complement while the other bears Fc receptors only and has no detectable receptors for complement. PWM appears to induce cytotoxicity in both T- and non-T-cell populations but the major cell type involved appears to be Fc receptor-bearing cells similar to those mediating antibody-dependent killing. It is concluded that PHA and antibody-dependent killing are the two most useful assays for discriminating between the cytotoxic activity of T and non-T cell in clinical studies.

Specificity of cell-mediated cytotoxicity against human melanoma lines: evidence for "non-specific" killing by activated T-cells

The specificity of cell-mediated cytotoxicity against melanoma cells in vitro has been analyzed in a large number of studies with cells both from normal and melanoma subjects. As in a number of other, recent, similar human studies, no evidence for tumour specificity was found. Effector cells in peripheral blood responsible for the cytotoxic raction were examined by cell separation methods based on red cell rosette formation and separation through Hypaque-Ficoll mixtures. The evidence suggests that non-specificity results from killing by cells separating largely in the non-sheep red blood cell rosetting fraction and which have cytotoxic specificity directed broadly to cells with abnormal membranes. Further analysis revealed that the cells were non-phagocytic and did not bear receptors for complement. They appear to be activated into cell division and to bear surface receptors for the Fc portion of IgG. Additional evidence is presented suggesting that the cells mainly responsible are activated thymus-dependent cells present in the circulation of both tumour-bearing and normal subjects.

Comparison of 51Cr release and microcytotoxicity assays against human melanoma cells

Comparisons of the cytotoxic activity of mononuclear cells from venous blood of human subjects against human melanoma cell lines have been made by means of the 51Cr release assay (CRA) and the microcytotoxicity assay (MCA) of Takasugi and Klein. The relative effectiveness of the two assays in the detection of killing by various sub-populations of effector cells was studied after depletion of monocytes and separation of the blood monocluear cells by SRBC receptor and Fc receptor resetting techniques. Overall, the results showed good correlation. Most differences were the result of low values recorded with the CRA when effector cells were obtained from Hypaque-Ficoll--separated populations which had not been further fractionated. These differences were largely removed when monocytes were depleted by glass absorption and may reflect interference with the CRA by monocytes. No consistent differences were found between the assays in the detection of killing by subfractions enriched for T cells or B cells in this tumour system. The MCA appears to offer the advantage of greater sensitivity and possibly detection of a wider range of cytotoxic mechanisms but the CRA has a number of advantages of a technical nature which make it more applicable to routine assays in clinical studies.

Referral letters from general practitioners

If continuity of care is to be preserved, then the process by which a patient is referred to hospital is important. We have analysed a series of letters of referral from general practitioners with special reference to the diagnoses made and the inclusion of a relevant history.

The cavity electrocardiogram in emergency artificial pacing

Effective temporary pacing was achieved using the cavity ECG as a guide in twenty-five of twenty-six patients, twenty of whom were too ill to be moved to the fluoroscope.

In all patients U.S.C.I. unipolar or bipolar electrodes were used and in eleven patients this method of pacing was applied during resuscitation; four patients survived to leave hospital.

This technique is described and is recommended for emergency pacing when a bedside image intensifier is unavailable.