Rapid detection of antibodies to immunoglobulin A molecules by using the particle gel immunoassay

BACKGROUND AND OBJECTIVES

Antibodies to immunoglobulin A (IgA) molecules are thought to be frequently responsible for anaphylactic reactions in transfusion medicine, but practical tests for the detection of antibodies to IgA are not yet available.

MATERIAL AND METHODS

Red, high-density polystyrene beads were coated with purified IgA molecules and then used to test serum samples collected from unselected healthy blood donors (n = 105) and patients with common variable immunodeficiency and/or IgA deficiency (n = 44). For testing, the standard gel-agglutination technique (ID-Micro Typing System) was employed.

RESULTS

None of the normal serum samples were reactive with IgA-coated beads and samples from only 10 patients were positive (titre range 1 : 2 to 1 : 256). Only one out of all patients studied had a history of an anaphylactic reaction and this was related to the administration of Rh(D) prophylaxis (anti-D immunoglobulin). The beads did not show non-specific agglutination and could be used repeatedly for longer than 6 months. The results were reproducible in all patients tested.

CONCLUSION

The new test allows a specific and rapid detection of antibodies to IgA molecules. In order to evaluate the clinical relevance of the test, analysis is required of a wider range of antibodies that produce anaphylactic reactions.

Sequence and specificity analysis of recombinant human Fab anti-Rh D isolated by phage display

BACKGROUND AND OBJECTIVES

Hyperimmune anti-Rh D serum is worldwide in short supply. As a first step to develop an alternative source of Rh D antibodies, we describe in this study the isolation and characterization of recombinant anti-Rh D Fab fragments.

MATERIALS AND METHODS

Peripheral blood mononuclear cells harvested from a hyperimmunized donor were used to construct two combinatorial Fab libraries. Phages expressing these Fab fragments were selected on whole red blood cells followed by testing of positive clones in an indirect hemagglutination assay.

RESULTS

Individual Fab clones are of high affinity and competitively inhibit the binding of a registered anti-D immunoglobulin. The Fab clones are also specific against the partial D phenotypes, Rh33, DIII, DIVa, DIVb, DVa, and DVII. The 13 different but highly homologous clones express preferentially VH3 segments.

CONCLUSION

These Fab fragments show potential for the development of a new generation of therapeutic anti-Rh D reagents.

Anti-D immunoglobulin in Rh(D) negative volunteers: clearance of Rh(D) positive red cells and kinetics of serum anti-D levels

Properties of a new anti-D immunoglobulin were assessed in Rh(D) negative healthy male adults. Six volunteers received intravenous, and five volunteers intramuscular injections of 200 micrograms anti-D, 48 hours after pre-treatment with 5 mL of Rh(D) positive erythrocytes. Immediately after intravenous administration of anti-D, a rapid decrease of the Rh(D) positive erythroyctes was noted. After intramuscular injection of anti-D, there was a lag phase of 6 hours until the erythrocytes decreased, and the elimination rate was slower. Twenty-four hours after injection of anti-D, the Rh(D) positive erythrocytes were at the detection limit or no longer detectable in all volunteers. After intravenous administration, anti-D serum levels decreased from 45 ng/mL at 2 hours to 29 ng/mL at 24 hours, whereas after intramuscular administration, anti-D became detectable at 4 hours and increased to 11 ng/mL at 24 hours. During subsequent months, anti-D serum levels decreased at similar rates in both groups. After six months, anti-D was not detectable in any of the volunteers. Thus, the new anti-D immunoglobulin induced elimination of the Rh(D) positive erythrocytes and suggested that Rh(D) immunization of the volunteers was prevented.

A low-incidence red cell antigen JAL associated with two unusual Rh gene complexes

A multilaboratory investigation during several years has identified a low incidence antigen JAL on the red cells of 7 propositi. JAL appears to be associated with two unusual Rh complexes, one of which produces a depressed C antigen and the other a depressed c antigen. Family studies strongly suggest that the JAL antigen is encoded by the RH locus. Anti-JAL has been implicated in haemolytic disease of the newborn and is thus considered to be a clinically significant antibody.

The red cell antigen JAL in the Swiss population: family studies showing that JAL is an Rh antigen (RH48)

The JAL antigen was found to have an overall frequency of 0.004% in the Swiss population and 0.06% in French-speaking Swiss. Family studies of 5 JAL+ individuals have shown that the JAL antigen is not part of the ABO, MNSs, Fy, Jk and Co blood group systems, or the Se system, nor is it X- or Y-linked. JAL is encoded by the RH locus or by a very closely linked locus. The number RH48 (4.48) has been assigned for JAL by the International Society of Blood Transfusion Working Party on Terminology for Red Cell Surface Antigens.