Abstract
The results obtained by Boyden 1 with the Libby photronreflectometer 2 indicate clearly the value of this instrument in studies of precipitin. The instrument affords an accurate measurement of the precipitate formed by antigen and antibody. Light rays passing through the turbid system are reflected by the suspended particles, and falling upon a photronic cell generate a current of electricity which is recorded by a galvanometer. The galvanometric readings, obtained with doubling dilutions of antigen and a constant amount of antiserum, furnish the points for a curve, the area under which is used to indicate the total reaction between the antigen and antiserum. A comparison of the areas of the homologous and heterologous reaction-curves is used herein to indicate the chemical similarity. In the interfacial tests, relationship-values were determined in the manner described by Boyden, 3 the end-point being the all-important factor.
The graphs show the results obtained when several antigens were tested with a diluted (1+2) anti-leghorn serum. Each antigen represents the pooled sera of from 4 to 95 birds, with the exception of turkey-buzzard which is the serum of one individual. In a similar manner the same antigens were tested with the precipitating antisera to the serum-proteins of turkey, guinea hen, duck, and pelican. The table shows the values obtained by the interfacial (ring) and nephelometric methods.
The injection of a mixture of antigens, such as serum, may result in the production of: (a) antibodies to one fraction alone; (b) antibodies to several or all fractions, with more to one fraction than to another. The fractions are rarely present in equal amounts, so the interfacial endpoints may, in some cases, be the result of one fraction and its antibodies, and in other cases the result of another fraction with its antibodies.
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