Forms of plastic solid phases

Separation of free immunoreactant from reactants immobilized on plastic is achieved simply by decanting, aspirating or retrieving the solution, in contrast to the often cumbersome techniques used in other systems (precipitation, chromatography, centrifugation, nonspecific adsorption on charcoal, talc or dextran). This simplicity has a direct, positive effect on the reproducibility and sensitivity of the assay. 

The forms of plastic supports for ElA may be varied beads, discs, tubes, plastic-coated toothpicks, matchsticks, and even cocktail stirrers (Shekarchi et al., 1982). Undoubtably, many other utensils could be used for this purpose. However, the most common supports are polystyrene or polyvinylchloride (PVC) microtitre plates with 12x8 wells of 0.3 ml. Although PVC plates may adsorb IgG more 

Pretreat plates with GA (0.25%), or poly-L-lysine (10 pg/ml), or phytohemagglutinin (PHA)-P (20 /Jg/ml Difco Laboratories) or anti-cell antibodies (20 pg/ml), using as coating solution Dulbecco s PBS, for 1 h at 37 C. 

Wash the cells extensively with Dulbecco s PBS and suspend a concentration of 1-5 X 10 cells/ml (depending on cell size). 

Add cell suspension to wells (shake often to prevent concentration differences) and centrifuge plates at 100 x g for 3 min. 

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