Activation of T cells in the blood of patients with acute malaria: Proliferative activity as indicated by Ki-67 expression

The expression of the proliferation-associated nuclear antigen Ki-67 in per ipheral blood mononuclear cells was studied in 30 patients with acute malar ial illness and 11 healthy controls from Addis Ababa or Nazareth in Ethiopi a. Seventeen patients had Plasmodium falciparum infections and 13 had Plasm odium vivax. Two-colour immunoenzymatic staining was developed in order to simultaneously detect the expression of the nuclear antigen Ki-67 and deter mine the surface phenotype of the cell. The median percentage of proliferat ing, Ki-67 positive lymphocytes was significantly higher in patients with a cute P. falciparum (11.8%) and P. vivax (15.6%) illnesses compared to the c ontrols (4.3%). The majority of Ki-67 positive cells were T cells (CD3(+)) while the relative increase of Ki-67 expressing cells was similar for both the CD4(+) and CD8(+) T-cell subsets. Our data show an increased number of activated cells driven to proliferation in the peripheral blood of patients during acute malaria illness.