Standardization of a micro-cytotoxicity assay for human natural killer cell lytic activity.

Cytotoxicity assays are widely used to evaluate the functional activity of NK and T cells against tumour target cells and the release of radioactive sodium chromate from labelled target cells is still the most commonly used marker of target lysis in culture supernatants. We describe here the standardization of a micro-cytotoxicity test in which the number of cytolytic effector and tumour target cells have been decreased by a factor of 10. The release obtained by 500 tumour target cells was compared with the release obtained by 5000 target cells in the standard cytotoxicity assay for target:effector cell ratios from 1:1 to 1:100. Both gamma and beta emissions of the 51Cr isotope were evaluated to determine the assay release. The results obtained by the micro-cytotoxicity assay (500 target cells) were comparable to those of the standard assay (5000 target cells) and 51Cr release evaluation using the gamma counter was the most sensitive method of determining lytic activity using 500 tumour target cells. beta counter evaluation using solid phase scintillation was found to be a reproducible alternative method, even if the lytic curves cannot be compared with those obtained using the traditional method.

Effect of aging on distribution and functional activity of GL183+ and EB6+ NK cells.

During aging an increased number of CD16+ lymphocytes and an impaired NK cell function have been demonstrated both in fresh and cloned NK cells obtained from the peripheral blood of elderly subjects. Recently, two novel surface molecules have been identified by GL183 and EB6 monoclonal antibodies on subsets of resting or activated NK cells. The expression of GL183 and/or EB6 identifies four distinct phenotypically stable NK subsets: GL183+EB6+, GL183-EB6-, GL183+EB6-, GL183-EB6+. Our study aimed at analyzing the distribution of GL183 and EB6 NK cell subsets in a group of elderly people and at establishing whether a different distribution of these NK lymphocyte subpopulations is related to the altered cytolytic activity found in the elderly. A broad individual variability in the percentages of CD16+GL183+ or CD16+EB6+ cells was observed. Nonetheless, the mean percentage of GL183+ cells in the elderly group showed a significant increase. The cytolytic activity of GL183+ and EB6+ sorted subsets showed a decrease that was almost equally distributed between the two subpopulations. Given the hypothesis of the ability of NK cells to discriminate between self and non self, the decreased cytolytic activity of GL183+ and EB6+ subsets could be related to a generally decreased ability of aging NK cells to recognize specific target cells.

Intravenous quinine therapy of hospitalized children with Plasmodium falciparum malaria in Kinshasa, Zaire.

To examine the clinical and parasitologic efficacy of quinine, we studied 34 children (7 months-13 years old) with severe or moderately severe Plasmodium falciparum infections. Quinine 10 mg/kg every 8 hr for 3 days was administered, initially by intravenous infusion of quinine formate followed by oral quinine dihydrochloride when tolerated. Thirty-three of the 34 patients were clinically well and had negative malaria smears 7 days after the initiation of therapy; 1 child, who presented in coma, died 29 hr after enrollment. The mean fever clearance time was 44.1 hr, and the mean parasite clearance time was 59.6 hr. A mean peak quinine level of 9.7 ppm was attained after the second dose of quinine, and the minimum concentration was maintained at 5-7 ppm during the 2nd and 3rd hospital days. In vitro testing was conducted with parasites from 10 patients: 9 isolates were resistant to chloroquine, and inhibition of schizont development with quinine occurred at a concentration of 8-32 pmol/well.