nature of the filtrate
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RED cells sensitized with an incomplete (blocking) anti-Rh antibody will agglutinate if suspended in serum1,2 or in concentrated albumin, or, having been washed, are exposed to an anti-human precipitating serum4. During an investigation in which the properties of red cells from cases of acute acquired hæmolytic anæmia were compared with red cells ‘changed’ by a filtrate of a broth culture of cholera vibrio, it was found that red cells previously sensitized by an incomplete antibody, and washed, were agglutinated after incubation with the cholera filtrate. Normal cells when so treated do not show any alteration until they are in contact with serum, when they show panagglutination as in the Hubener Thomsen phenomenon. The ‘T’ agglutinin responsible for the panagglutination is present in all normal sera and can be specifically absorbed by ‘changed’ cells; when incomplete anti-Rh sera are so absorbed and incubated with red cells, together with cholera filtrate, they show specific agglutination of Rh-positive cells. These reactions are shown in the accompanying table.