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Dizygotic monochorionic twin pregnancies can result in blood chimerism due to in uterotwin‐to‐twin exchange of stem cells. In this case, we examined the proportion of allogeneic red blood cells by flow cytometry and the proportion of allogeneic nucleated cells by digital polymerase chain reaction at 7 months and again at 5 years. We found an increase in the proportion of allogeneic cells from 63% to 89% in one twin, and a similar increase in autologous cells in the other twin from 57% to 84%. A paradigm for stem cell therapy could be modeled on this case: induction of tolerance and chimerism by antenatal transfusion of donor stem cells. The procedure would hold the promise of transplantation and tolerance induction without myeloablative conditioning for inheritable benign hematological diseases such as sickle cell disease and thalassemia. A substantial chimerism present at delivery and spontaneously increasing indicates that antenatal transfusion of stem cells could be a treatment for inheritable benign hematological diseases.

The soluble amphiphilic glycoprotein, Ag1 (gp60), purified from supernatants of in vitro cultures ofPlasmodium falciparum has a molecular mass of 60 kDa and did not exhibit size variation in the differentP. falciparum isolates tested by immunoblotting. Ag1 was shown to interact with the lectinErythrina christagalli agglutinin, which is specific for carbohydrates bearing ß-d-galactose(1–4)-d-N-acetylglucosamine. Indirect immunofluorescence studies showed that Ag1 is located on the surface of trophozoites and schizonts but not on the surface of merozoites. Ag1 is recognized by human immune sera from six different malaria-endemic regions. Ag1 induces in vitro proliferation of lymphocytes from malaria-immune individuals in an antigenspecific manner.

The aims of the present study were to describe the age-related immunoglobulin M (IgM) and IgG response to part of a 220-kDa glutamate-rich protein (GLURP) from Plasmodium falciparum and to determine possible correlations of possession of these antibodies with malaria morbidity. IgM and IgG levels were measured with a recombinant fusion protein consisting of the carboxy-terminal 783 amino acids of the GLURP. Samples for the study were obtained during a longitudinal malaria morbidity survey performed in The Gambia; cross-sectional surveys were performed at the beginning of the transmission season in May and in October. Seropositivity rates increased with age to a maximum of 77% for IgM and 95% for IgG in adults. High prevalences of seropositivity were associated with certain human leukocyte antigen class II alleles (DRw8, DR9, DR7, DR4, DQw7, and DQw2) or haplotypes. The relationship between anti-GLURP489-1271 antibodies and clinical immunity is not clear; asymptomatically infected children aged 5 to 8 years had significantly higher levels of IgG than clinically ill children of the same age, suggesting that antibodies to the carboxy-terminal part of the GLURP may contribute to immunity to P. falciparum. However, this was not significant for younger children.

Two seroepidemiological studies were performed in an area of Burkina Faso hyperendemic for malaria to estimate the protective role of immunoglobulin M (IgM) antibodies. Six cross-sectional surveys were carried out on children (ages, < 16 years) in the village of Karankasso. The evolution of antibodies to crude extracts of Plasmodium falciparum (IgG or IgM antisomatic and IgG antiexoantigens) were tested by IFI or enzyme-linked immunosorbent assay and were followed up according to the fluctuations of the parasite densities. Specific IgG antibodies had the same evolution as parasite densities. By contrast, specific IgM antibodies increased when IgG and parasite densities began to decrease (despite a high inoculation rate). A longitudinal survey of 77 children and adults was conducted in another village (Dafinso). In that study, clinical follow-up of the selected individuals allowed us to define three groups in the population. Children in group 1 were considered nonimmune (children with one or more malaria attacks). Group 2 was composed of semiimmune children who did not present with any malarial attack during the survey but who had high levels of parasitemia during the transmission period. Group 3 was composed of immunoprotected adults. Specific IgM and IgG antibodies to crude extracts or a recombinant antigen (glutamate-rich protein) of P. falciparum were tested. Specific IgM antibodies were lower in group 1 (nonimmune) than in groups 2 (semiimmune) and 3 (immunoprotected). Furthermore, there was a negative correlation between parasite densities and the levels of specific IgM antibodies. We discuss the possible role of IgM antibodies in the acquisition of immunity to malaria.