Peripheral blood mononuclear and polymorphonuclear cells have been demonstrated to kill and inhibit malaria parasite proliferation in vitro, but most of the reports required activation of the cells by cytokines or presence of immune sera or opsonins. In our study, peripheral blood leukocytes from non-immune donor efficiently inhibited Plasmodium falciparum growth, depending on the effecter/target ratio. Moreover, these cells produced a large amount of interlenkin-8 (IL-8) under stimulation with infected erythrocytes or supernatant of the Plasmodium falciparum culture. IL-8 secretion in the culture supernatant of polymorphonuclear cells was noted from 6-9 hr of stimulation with the parasites, with a substantial increase over 24 hours of culture. Attempt to elucidate whether IL-8 was involved in malaria suppression was done, and the result suggested that IL-8 was not directly involved in the anti-malarial activity of the mononuclear and polymorphonuclear cells. The other mechanism besides IL-8 may work for inhibiting parasite growth in the culture system of malaria parasites associated with leukocytes.

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A stool examination revealed oocysts of Cyclospora cayetanensis in a 54-year-old Japanese man who had recently returned from the Phillipines. He suffered from watery diarrhea for about two weeks prior to visiting our hospital. An oral dose of 1, 600 mg sulfamethoxazole and 320 mg trimethoprim was administered daily for nine days, and his diarrhea had disappeared by the fifth day of medication. Most Japanese physicians and laboratory technicians are unfamiliar with this protozoan disease, and need to be reminded of its existence when they encounter patients with diarrhea who have recently returned from a cyclosporiasis endemic area.

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The antimalarial activity of the hot-water extract of leaves and roots of Dichroa febrifuga was evaluated against Plasmodium yoelii 17XL in ICR mice. Untreated control mice died with a gradual body weight loss and increase of parasitemia by day 9 after infection. The hot-water extract of leaves collected in June showed an antimalarial activity, and furthermore the possible adverse side effect was also observed. All mice given orally the extract of leaves (0.1 g/ml) collected in June died by day 9 without parasite multiplication. The mice given the lower concentration (0.025 g/ml) of the same leaf extract showed low parasitemia levels during administration. Following a transient increase of malaria parasites in the bloodstream, no parasites could be detected by a microscopic examination, and all mice survived during the experiment. On the other hand, the extract of leaves (0.1 g/ml) collected in December showed no activity. The extract of roots (0.1 g/ml) of D. febrifuga collected in December, however, had an antimalarial activity, and three mice out of four survived during the experiment. The leaves collected in June contained about 30 times as much febrifugine and isofebrifugine mixture as those in December.

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