Search

Blood B lymphocytes obtained from Plasmodium falciparum-immune Saimiri monkeys were assayed for their in vitro differentiation in immunoglobulin-secreting cells upon restimulation with P. falciparum-parasitized Saimiri red blood cells. Selected culture conditions enabled appropriately stimulated blood B cells to secrete 3F11/G10+ IgG, detected in the supernatants by means of a dot immunobinding assay. Primed blood B lymphocytes from P. falciparum-immune Saimiri monkeys were thus able to secrete IgG when restimulated by parasitized red blood cells in the presence of T cell- and monocyte-derived cytokines (recombinant human cytokines). These primed blood B cells, which were able to differentiate, were shown to secrete antibodies reactive with P. falciparum-infected red blood cells, as detected by means of an indirect immunofluorescence assay, and reactive with P. falciparum-infected red blood cell extracts, as detected by means of Western blot analysis. Furthermore, due to the possibility of discriminating between IgG subtypes in the squirrel monkey (3F11/G10+::3A2/G6+ IgG [associated with protection against the blood stages of P. falciparum] vs. 3F11/G10+::3E4/H8+ IgG [usually not functionally associated with protection]), we have attempted to estimate the respective proportions of each IgG subtype. In defined culture conditions, Saimiri monkey blood B cells preferentially secrete 3F11/G10+::3E4/H8+ IgG in response to parasitized red blood cells. We therefore discuss the conditions that would render this assay suitable for the selection, among P. falciparum blood stage antigens, of those that have major B-cell epitopes.

We report here on functional aspects of squirrel monkey T cells isolated either from peripheral blood mononuclear cells or in the presence of accessory cells or accessory-cell-secreted cytokines. The T-cell response triggered by polyclonal activators was measured through proliferation, T-cell growth factor production and transient expression of receptors to growth factors. We also sought to delineate mechanisms by which antimitogenic molecules might prevent lymphocytes from being able to express "activation antigens" and/or from proliferating. Under these conditions, we mainly explored the inducible IL2/IL2R pathway and phenomena occurring in lymphocyte "non-activation" in terms of early and late cellular events; indeed, defects in the IL2/IL2R pathway represent one of the dysregulation events presumed to occur during the acute phase of human malaria, disease for which. Saimiri monkeys have been selected as experimental hosts.

Characterization and functional aspects of squirrel monkey peripheral blood mononuclear cells (PBMC), and mainly T cells, are described in the present paper; this should enable the study of cellular immune responses in an experimental model for malaria. PBMC were obtained from Ficoll-Hypaque gradient separation and fractionated into T cells and non-T cells by means of E-rosetting techniques and adherence to plastic dishes. PBMC subset phenotypes were characterized by means of monoclonal antibodies (mAb) directed against human leukocyte differentiation antigens (Ag), fluoresceinated lectins, anti-surface Ig (squirrel-monkey-specific) antibodies (Ab) and latex bead ingestion assays. PBMC functions were assayed through lymphoblastic transformation tests (LTT) in the presence of either numerous mitogenic, comitogenic and anti-mitogenic lectins or anti-human leukocyte differentiation Ag mAb. We sought to standardize reference values for lymphocyte phenotypes and functions in normal squirrel monkeys (prior to experimental infection). We also present evidence that splenectomy (generally rendered necessary for experimental human malaria infection) performed six months prior to the present investigation did not modify PBMC numbers and functions in the tested animals.