Neonatal thrombocytopenia in HLA-DR, -DQ, -DP-typed mother due to rare anti-HPA-1b (PLA2) (Zwb) fetomaternal immunization.

A new case of rare neonatal alloimmune thrombocytopenia, due to an IgG anti-HPA-1b in a mother HPA-1 (a+, b-), was diagnosed using monoclonal antibody-specific immobilization of platelet antigens. Clinically, it was similar to the 2 previously reported observations and confirmed that, in this particular case of anti-HPA-1b, the treatment with random platelet pools may be as effective as selected single-donor platelet units when maternal platelets are unusable. The HLA-DR, -DQ, -DP genotypes of the family were obtained by PCR-SSO. The mother's typing, compared to the HLA-DR of the 6 similar cases reported in Europe, suggests that a combined effect of two rare HLA haplotypes might enhance this immunization.

[Platelet group polymorphism in Provence. Comparison with the frequencies of platelet-specific allo-antigens observed in other populations]. / Polymorphisme des groupes plaquettaires en Provence. Comparaison avec les fréquences des allo-antigènes spécifiques plaquettaires observées dans les autres populations.

Systems HPA-1 (Pla); HPA-3 (Bak) HPA-5 (Br) are involved in neonatal alloimmune thrombocytopenia and post-transfusion purpura. The frequencies of platelet-specific antigens in these three systems have been studied among one hundred one unrelated blood donors from Provence (South of France) for three generations. Typing was performed by the MAIPA test (monoclonal antibody-specific immobilization platelet antigen). The phenotypes frequencies found were: HPA-1a (PlA1): 97%; HPA-3a (Baka): 88.1%. These frequencies are quite similar to those reported in Europe and North America, but are different compared to Oriental and South American populations. Our Provence population has the highest frequency of HPA-5b (Bra) yet reported: 23.8%. These results define the polymorphism of platelet-specific antigens in the Provence population. Similar studies, among other populations, would provide new data for geographical haematology, which has so far been based on erythrocyte, leucocyte and serum polymorphisms. The variations between populations in these platelet-specific polymorphisms would be so many useful descriptive elements for the epidemiological study of associated diseases.

[Platelet antibody activity in malaria thrombocytopenia]. / Activité anticorps antiplaquettaire dans la thrombopénie palustre.

To assess immune responses to malaria-induced thrombocytopenia, an haematologic and immunologic study was performed on 25 patients with imported malaria upon admission and 8 days after treatment. Thrombocytopenia (150 x 10(9)/litre) was detected in 19 cases (P. falciparum: 11 cases, P. ovale: 6 cases, P. vivax: 2 cases). No laboratory evidence of disseminated intravascular coagulation impairment was found in any of the patients. Bone marrow examination performed in 9 cases showed no abnormality in the megakaryocyte series. Platelet count was independent of circulating parasite levels (r = 0.27) and inversely related to the number of antibody binding sites (ABS) on platelets (r = -0.6, p. less than 0.01). The indirect Coombs test (r = -0.54; p less than 0.01) and IgG and IgE levels (p less than 0.02) gave similar findings. A statistical correlation was observed between the level of circulating immune complex and the number of ABS (r = 0.525, p less than 0.01). Thus malaria-induced thrombocytopenia seems to mainly involve IgG type antiplatelet antibody activity. Although they may be implicated in the binding of antibodies to platelets, circulating immune complexes do not appear to mediate thrombocytopenia.

IgM antiplatelet antibodies in 7 out of 20 rheumatoid arthritis sera. A new antiplatelet antibody ELISA. Reverse correlation with anti-B-lymphocyte antibodies in the same sera.

In a previous work, we had found that anti-B lymphocyte antibodies exist in rheumatoid arthritis. To investigate whether these antibodies were directed against surface immunoglobulins or not we have investigated if RA sera could recognize similar structures on other targets such as platelets (on which immunoglobulins and immune complexes are present) by a new ELISA method. No IgG antiplatelet antibody was found in 20 RA sera. But 7 out of these 20 RA sera had IgM antiplatelet antibodies when tested on platelets from 5 donors. The comparison of the positivities of these sera on B lymphocytes and platelets from the same donors showed a statistically significant reverse (X2 = 20,008, p much less than 0.0001) correlation. The target antigen and the meaning of these IgM antiplatelet antibodies, which seem to be associated with severe RA, is still under investigation.

[Antiplatelet antibodies of the IgM class detected by ELISA in the serum of 20 patients with rheumatoid polyarthritis. Inverse correlation with the presence of anti-B lymphocyte antibodies]. / Anticorps antiplaquettes de classe IgM détectés par ELISA dans le sérum de 20 malades atteints de polyarthrite rhumatoïde. Corrélation inverse avec la présence d'anticorps antilymphocytes B.

In an earlier study, the authors demonstrated IgM anti-B lymphocyte antibodies in the sera of patients with rheumatoid arthritis. In an attempt to identify the target antigen, we studied the reactivity of these same sera to other cells, by means of a recently developed ELISA micro-method. 7 of the 20 sera contained IgM anti-platelet antibodies. There is an inverse correlation between the presence of anti-platelet antibodies and anti-B lymphocytes antibodies. The detection of anti-platelet antibodies in the serum of patients with rheumatoid arthritis may correspond to the recognition of aggregated immunoglobulins or specific immune complexes bound to receptors on the surface of the platelets.