Dynamics and kinetics of natural killer cell cytotoxicity in human malaria as evaluated by a novel stepwise cytotoxicity assay

Malaria causes important functional alterations of the immune system, but several of them are poorly defined. To evaluate thoroughly the natural killer cell cytotoxicity in patients with malaria, we developed a technique capable to assess both the dynamics and the kinetics of the process. For the kinetics assay, human peripheral blood mononuclear cells were previously incubated with K562 cells and kept in agarose medium, while for the dynamics assay both cells were maintained in suspension. NK activity from patients with vivax malaria presented a kinetics profile faster than those with falciparum malaria. NK cytotoxicity positively correlated with parasitemia in falciparum malaria. The dynamics of NK cytotoxicity of healthy individuals was elevated at the beginning of the process and then significantly decreased. In contrast, malaria patients presented successive peaks of NK activity. Our results confirmed the occurrence of alteration in NK cell function during malaria, and added new data about the NK cytotoxicity process.

A malária causa importantes alterações do sistema imunitário, muitas ainda mal definidas. Para permitir uma avaliação abrangente da atividade citotóxica das células natural killer em pacientes com malária, desenvolvemos um teste capaz de avaliar concomitantemente a dinâmica e a cinética do processo. Para a avaliação da cinética, células mononucleares do sangue periférico interagiram com células K562 e foram mantidas em agarose, enquanto para avaliar a dinâmica as células eram mantidas em suspensão. A cinética da atividade citotóxica das células NK foi mais rápida em pacientes com Plasmodium vivax, do que naqueles infectados com P. falciparum. Nestes, houve correlação positiva entre a atividade citotóxica das células NK e a parasitemia. O padrão da dinâmica da atividade citotóxica nos pacientes com malária foi bem diferente daquele apresentado pelos indivíduos sadios. Enquanto nestes, a atividade estava muito aumentada no início da incubação das células, sofrendo posteriormente uma redução, nos indivíduos infectados foram detectados sucessivos picos de atividade citotóxica. Nossos resultados confirmam a ocorrência de alteração funcional das células NK na malária humana e acrescentam novos dados sobre a dinâmica e a cinética da atividade citotóxica.

Increase of NKG2D ligands and sensitivity to NK cell-mediated cytotoxicity of tumor cells by heat shock and ionizing radiation

In this study, we have investigated if current cancer therapeutic modalities including hyperthermia and ionizing radiation can increase the expression of NKG2D ligands in human cancer cell lines. The expressions of NKG2D ligands were induced by both heat shock and ionizing radiation in various cell lines including KM12, NCI-H23, HeLa and A375 cells with peaks at 2 h and 9 h after treatment, respectively, although inducibility of each NKG2D ligand was various depending on cell lines. During the induction of NKG2D ligands, heat shock protein 70 was induced by heat shock but not by ionizing radiation. These results were followed by increased susceptibilities to NK cell-mediated cytolysis after treatment with heat shock and ionizing radiation. These results suggest that heat shock and ionizing radiation induce NKG2D ligands and consequently might lead to increased NK cell-mediated cytotoxicity in various cancer cells.

Citolisis natural en sujetos infectados por VIH-I: alteración de la activación de las células natural killer / Natural cytolysis in HIV-1 infected individuals: alteration in the activation of the natural killer cells

Las células Natural Killer (cél NK), linfocitos efectores de actividad citolítica natural, son críticas en la defensa antiinfecciosa. En la infección por VIH-I se ha descrito una disminución de la actividad citolítica NK; sin embargo, se desconocen los mecanismos involucrados, por lo que el objetivo de este trabajo fue estudiar la ACNK y la acción in vitro de inmunomoduladores para intentar explicar esta deficiencia. Se analizaron 20 individuos infectados por VIH-I (10 asintomáticos y 10 con SIDA) y 30 individuos seronegativos como controles. La ACNK se determinó utilizando cél K-562 radiomarcadas con 51-Cr (cromato de sodio) como cél blanco y cél mononucleares periféricas como cél efectoras, expresándose los resultados como por ciento de Lisis específica. En cultivos in vitro, se analizó el efecto de inmunomoduladores sobre la ACNK: interleuquina-2 (IL-2, 25 U/mL), interferon-alfa (IFN-a, 500 U/mL) y la acción conjunta de ionófor de calcio A23187 (lo, 10.0 uM) más un éster de forbol (TPA, 250 ng/mL)(Io+TPA). El análisis fenotípico, CD 16+/56+ se efectuó por citometría de flujo con Ac monoclonales fluorescentes (Becton Dickinson)

Participación de la apoptosis en los procesos inmunológicos / Participation of apoptosis in immunologic processes

Apoptosis is a biological process that leads certain cells to die in a controlled fashion. Its biochemical manifestation is DNA fragmentation due to the action of an endonuclease and morphological consequences is the formation of apoptic bodies, seen with lught or electron microscopy. Apoptosis is universally important in embryogenesis and morphologenesis of all tissues. Lately, a fundamental role of apoptosis in the physiology and physiopathology of immunological events has been uncovered. This review details the role of apoptosis in the development of auto-tolerance, immunological memory and AIDS pathogenesis

Immunosuppression by human seminal plasma as evaluated by effect on natural killer cell cytotoxicity.

Re-examination of earlier observations of the suppressive role of oxidized polyamines and their cytotoxic products, has suggested that immunosuppression by seminal plasma (SePl) observed in in vitro assays employing culture medium supplemented with serum containing amine oxidase is 'artefactual'. Investigation of the relevancy of this suggestion to immunosuppression of natural killer (NK) cell activity by SePl as related to NK cell viability was made. NK cells in various culture regimens were preincubated in SePl and medium supplemented with 10 per cent foetal bovine serum, a source of amine oxidase, without and with 0.2 mM hydroxylamine, an amine oxidase inhibitor, and 10 per cent normal human AB serum, virtually devoid of amine oxidase, and examined for viability up to 72 h by trypan blue dye exclusion and lytic activity in a 4 h 51chromium-release microcytotoxicity assay. Viability to NK cells varied with the concentration of SePl, culture medium and time of incubation. At 18 and 24 h, times corresponding to preincubation and completion of the NK cell assay, viability was greater than or equal to 75 per cent for the optimum inhibitory concentration of SePl, irrespective of the culture medium. Comparison of the lytic activity of NK cells preincubated with the optimum inhibitory concentration of SePl in the various culture regimens did not disclose significant (P less than 0.05) differences.(ABSTRACT TRUNCATED AT 250 WORDS)