Hemagglutination inhibition technique

Practicability. The radioimmunoassay is easy to perform, and unlike the hemagglutination-inhibition technique, requires only small amounts of purified gonadotropic hormones. The main disadvantage of radioimmunoassays is that they require costly equipment and laboratories which are specially constructed for the handling of relatively large quantities of isotopic iodine. 

In indirect or passive hemagglutination, the erythrocytes are used as a particulate carrier of foreign antigen (and in some tests of antibodies) this technique has wide applications. Other materials available in the form of fine particles, such as bentonite and latex, also have been used as antigen carriers, but they are more difficult to coat, standardize, and store. In a related variation of tliis technique, known as hemagglutination inhibition, the ability of antigens, haptens, or other substances to specifically inhibit hemagglutination of sensitized (coated) cells by antibody is determined. 

Wide and his colleagues (W5, W7) were the first to apply the technique of hemagglutination-inhibition to the estimation of urinary LH. They found that some antisera raised against HCG were incapable of distinguishing between HCG and LH, and, accordingly, they were able to establish an assay system for LH using an antiserum raised to HCG and HCG-coated red blood cells. Taymor (T2) used a similar system to assay human urinary LH. He also employed an HCG antiserum and latex particles coated with this hormone the system was specific in that a cross reaction with ovine LH was not observed however, its specificity with respect to FSH was not reported. Taymor (T2) found it necessary to extract LH from urine prior to immunoassay. For this purpose he preferred precipitation with acetone to treatment with alcohol, since trace amounts of the latter interfered with the antigen-antibody reaction. 

Precision. Figures for the index of precision (A) using such techniques do not yet appear to have been calculated. According to Stockell and Hartree (S25), the precision of hemagglutination-inhibition tests is reasonably satisfactory in skilled hands, the fiducial limits of... 

Discussion of the effect of ligand structure on protein-carbohydrate affinity requires an evaluation of complex stability constants. A munber of biophysical techniques are appropriate for the study of protein-carbohydrate interaction many of the more enlightening strategies are the topics of separate chapters elsewhere in this volume. We describe below three techniques used extensively in glycobiology— inhibition of hemagglutination, enzyme-linked lectin assay (ELLA), and isothermal titration microcalorimetry—and we consider the types of information provided by each technique in order to facilitate appropriate interpretation of the data. 

---