Development of non-agglutination microarray blood grouping.

Microarray technology provides an opportunity to monitor multiple parameters simultaneously. High-throughput applications such as blood donation screening could greatly benefit from performing various tests on a single testing platform. Blood grouping represents one part of the donation testing complementing the screening for blood-borne pathogens. Blood group serology traditionally exploited agglutination as the detection method. In this investigation, we have adapted blood grouping reactions to a solid-phase microarray substrate in a non-agglutination reaction format as an initial step in the development of a combined microarray testing platform. We have investigated immobilization of proprietary antibodies on multiple surfaces and monitored their performance under various reaction conditions. For the first time, highly specific blood grouping has been achieved on a planar microarray using directly labelled erythrocytes or a secondary labelled reagent using fluorescent signal end point readout. We have also complemented microarray data with a label-free, surface plasmon resonance-based Biacore platform data and used the real time quantitative measurement to rank anti-A antibodies according to the strength of reaction with the immobilized synthetic blood group antigen A.

An unusual anti-H lectin inhibited by milk from individuals with the Bombay phenotype.

There are several lectins with anti-H specificity but few of them serve as useful reagents. An anti-H lectin, extracted from the seeds of the plant Momordica dioica Roxb. ex willd., was tested for its hemagglutination and inhibition properties, using standard serologic methods and panel RBCs, serum, saliva, milk, and oligosaccharides purified from milk. The extract displayed strongest agglutination with group O RBCs and was weakest with group A1B RBCs in a spectrum of O>A2>B>A2B>A1>A1B; the extract failed to react with the RBCs from 25 individuals with the Bombay (Oh) phenotype and was inhibited by H secretor saliva, hence it was characterized as anti-H. However, its inhibition by milk samples from five mothers with the Bombay phenotype called into question its specificity as anti-H. The lectin reacted as strongly with group O ii (adult) RBCs as with normal OI RBCs, ruling out its specificity as anti-HI. Hemagglutination inhibition was observed with 2'-fucosyllactose (Type 2 H) and lacto-N-fucopentose-I (Type 1 H), suggesting that the binding of the lectin had preference for H structures. However, inhibition by N-acetyllactosamine, lacto-Ntetraose, and lacto-N-neotetraose suggested that the lectin also recognized unsubstituted terminal beta-linked galactose units. The hemagglutinin property in the present lectin showed an unusual anti-H specificity. The lectin was inhibited by milk from Bombay phenotype individuals and certain milk oligosaccharides not specific for the H antigen.