ACUTE PLASMODIUM-FALCIPARUM INFECTION IS ASSOCIATED WITH INCREASED PERCENTAGES OF APOPTOTIC CELLS

The impact of acute malaria infection on the level of spontaneous apop tosis, i.e., the percentage of apoptotic cells detectable in lymphocyt es cultured without any exogenous stimulus for 3 days in vitro, was ev aluated. Quantitation of apoptosis was performed by staining of lympho cyte nuclei with propidium iodide and analysis of the fluorescence by cytometry. The mean apoptosis of 23 HIV-negative patients (15 Africans and 8 Europeans) determined during a confirmed Plasmodium falciparum attack was 27.2% (95% confidence interval (CI) = 23.5-30.7%) i.e., 2.2 times the mean level found in 49 controls (12.4%, CI = 11.1-13.6). Th ese controls included age- and sex-matched Africans (n = 37) and Europ eans (n = 12) differing only by their previous level of exposure to P. falciparum. Naive (European) as well as previously exposed (African) subjects showed dramatically elevated levels of spontaneous apoptosis during the malaria attack (mean = 22.5%, CI = 20.7-24.4 for Europeans; mean = 29.7%, CI = 24.6-34.7 for Africans). Such unusually raised lev els were observed for at least 1.5 months and were probably detectable for longer periods as suggested by the fact that the mean level of sp ontaneous apoptosis in healthy Africans was basically higher (13.8%, C I = 12.5-15) than the one found in healthy Europeans (8.2%, CI = 6.3-1 0.1) (P = 0.0001). Selective immunomagnetic cell isolations carried ou t immediately before apoptosis quantitation showed that this process a ffected not only the alpha beta T cells (CD4(+) T cells as well as CD8 (+) T cells) but also the gamma delta T cells and the B-lymphocyte sub set. Of particular interest, blastic cells were reduced when apoptosis was elevated, suggesting that both resting and activated cells could be involved in this process.