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ABSTRACT: Thrombocytopenia is detected in around one percent of newborns. In otherwise healthy term newborns, thrombocytopenia is most often caused by alloantibodies transferred from the mother to the foetus. In the Caucasian populations human platelet antigen (HPA)-1a is the most immunogenic HPA. In Japan and China antibodies in the HPA-4 system are the most frequent cause of FNAIT. The immune response against the HPA must be understood in order to avoid immunization or prevent induction of FNAIT where mothers are already immunized.
ISBT Science Series 10/2011; 6(2):261 - 264.
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ABSTRACT: Background The immune system is educated to detect and react with foreign antigens and to tolerate self-antigen. Transfusion of blood cells and plasma and pregnancies challenge the immune system by the introduction of foreign antigens. The antigens may cause an immune response, but in many instances this is not the case and the individual is not immunised after exposure of blood group antigens.Aims The aim of the presentation is to dissect some immune responses to blood group antigens in order to understand the mechanism of immunisation.Methods The results of immune responses to blood group antigens can be detected by the presence of antibodies to the antigens. If the antibodies are of IgG class, the activated B cells have received help from antigen specific T cells. Both antibodies, B cells and T cells can be isolated from immunised individuals and studied in the laboratory. Also B-cell receptors and T-cell receptors as well as MHC molecules on antigen presenting cells can be studied and models of the immune synapses can be created in vitro.Results The most classic immune responses in transfusion medicine and in incompatible pregnancies are immune responses to the RhD antigen on red cells, HLA class I molecules on white cells and platelets and human platelet antigens. The nature of these antigens are different; RhD antigens are part of a large complex, present on red cells from RhD positive individuals and completely lacking on red cells from RhD negative individuals. It is likely that many peptides derived from this antigen complex may stimulate T cells and B cells. HLA antigens are highly polymorphic and the antigens are known to induce strong alloimmune responses. The HPA antigens are created by one amino acid difference in allotypes based on a single nucleotide polymorphism at the genetic level. HPA 1a induce immune responses in 10% of HPA 1b homozygote pregnant women. The result of these immune responses is destruction of blood cells with clinical consequences connected to the effect of transfusions or the outcome of pregnancies.Summary/Conclusions Even though there is emerging knowledge about the immune responses to some of the blood group antigens, more information must be gained in order to understand the complete picture. The action of the innate immune response initiating the adaptive immune response to blood group antigens is not well understood. A detailed understanding of both the innate ad the adaptive part of the immune response is necessary to identify individuals at risk for immunisation and to prevent immunisation to blood group antigens.
ISBT Science Series 06/2010; 5(n1):24 - 26.
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ABSTRACT: Controversies regarding the pathophysiology of neonatal alloimmune thrombocytopenia (NAIT) has hampered the development of consensus about how to identify, follow up and treat the women and children with this serious complication. One reason for this is that knowledge about the condition derived from previous retrospective studies do not necessarily conform with data derived from prospective investigations. The main obstacle to introduction of general screening programs to identify the pregnancies to treat, have been lack of reliable risk factors, and an effective treatment. Now, several recent prospective screening programs including up to 100,000 pregnant women has changed the understanding of the NAIT-pathology, and has shown that we are close to answering these critical questions.
Scandinavian Journal of Immunology 12/2009; 70(6):531-4. · 2.23 Impact Factor
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BJOG An International Journal of Obstetrics & Gynaecology 01/2008; 115(3):413 - 414. · 3.41 Impact Factor
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H H H Kanhai,
L Porcelijn,
C P Engelfriet,
H W Reesink,
S Panzer,
B Ulm,
M Goldman,
I Bonacossa,
L Richard,
M David, [......],
L T N Osnes,
A Husebekk,
M K Killie, J Kjeldsen-Kragh,
B Zupanska,
E Muñiz-Diaz,
N Nogués,
J Parra,
S J Urbaniak,
A Cameron
Vox Sanguinis 12/2007; 93(4):370-85. · 2.86 Impact Factor
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R N I Pietersz,
C P Engelfriet,
H W Reesink,
E M Wood,
S Winzar,
A J Keller,
J T Wilson,
G Henn,
W R Mayr,
S Ramirez-Arcos, [......],
E Cadden,
W G Murphy,
M Satake,
D de Korte,
V Bosnes, J Kjeldsen-Kragh,
C McDonald,
M E Brecher,
R Yomtovian,
J P AuBuchon
Vox Sanguinis 11/2007; 93(3):260-77. · 2.86 Impact Factor
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ABSTRACT: To estimate the costs and health consequences of three different screening strategies for neonatal alloimmune thrombocytopenia (NAIT).
Cost-utility analysis on the basis of a decision tree that incorporates the relevant strategies and outcomes.
Three health regions in Norway encompassing a 2.78 million population.
Pregnant women (n = 100,448) screened for human platelet antigen (HPA) 1a and anti-HPA 1a antibodies, and their babies.
Decision tree analysis. In three branches of the decision tree, pregnant women entered a programme while in one no screening was performed. The three different screening strategies included all HPA 1a negative women, only HPA 1a negative, HLA DRB3*0101 positive women or only HPA 1a negative women with high level of anti-HPA 1a antibodies. Included women underwent ultrasound examination and elective caesarean section 2-4 weeks before term. Severely thrombocytopenic newborn were transfused immediately with compatible platelets.
Quality-adjusted life years (QALYs) and costs.
Compared with no screening, a programme of screening and subsequent treatment would generate between 210 and 230 additional QALYs among 100,000 pregnant women, and at the same time, reduce health care costs by approximately 1.7 million euros. The sensitivity analyses indicate that screening is cost effective or even cost saving within a wide range of probabilities and costs.
Our calculations indicate that it is possible to establish an antenatal screening programme for NAIT that is cost effective.
BJOG An International Journal of Obstetrics & Gynaecology 06/2007; 114(5):588-95. · 3.41 Impact Factor
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ABSTRACT: Results from a study of more than 100 000 pregnant women show that the pathophysiology of neonatal alloimmune thrombocytopenia (NAIT) and haemolytic disease of the newborn (HDN) has many equalities [1]. It has been reported that NAIT is more than three times more frequent compared with HDN. This makes it tempting to consider a design for screening for HPA 1a negativity and follow up in/after the pregnancy based on the same principles as for RhD-negative pregnant women. Even without available vaccination, it is strongly indicated that screening and Caesarean section 2–4 weeks prior to term in mothers with the HPA-1a-negative platelet type, reduce neonatal morbidity and mortality due to NAIT.
ISBT Science Series 05/2007; 2(1):111 - 113.
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C P Engelfriet,
H W Reesink,
M A Blajchman,
L Muylle, J Kjeldsen-Kragh,
R Kekomäki,
R Yomtovian,
P Höcker,
G Stiegler,
H G Klein,
K Soldan,
J Barbara,
A Slopecki,
A Robinson,
H Seyfried
Vox Sanguinis 02/2000; 78(1):59-67. · 2.86 Impact Factor
