Specific antibodies and heterologous antigensin monofactor sera.
A concentrated monofactor serum 9 (Wellcome lot K 8028) precipitated against proteins from 2 different strains of Salmonella enteritidis and from a strain of S. dublin, as well as against the proteinic moiety of the somatic antigen from S. typhi 0 901; no polysaccharide from the strains, sharing factor 9, precipitated against this serum. A concentrated monofactor serum 20 (Wellcome lot K 6733) precipitated against the proteins from S. emek (8, 20), but not against its polysaccharide. A monofactor serum 8 (Wellcome lot K 7801), different from a lot previously analysed (Wellcome lot K 6860), precipitated against the same proteins as the previous lot, but, in addition, precipitated strongly against the polysaccharide of S, newport (6.8) and weakly with the polysaccharide of S. emek too. According to these and previous results, it is not clear what sort of antibodies responsible for cross-agglutination are absorbed by the heterologous strains used in the operations. Since more often than not antipolysaccharide antibodies were not found in concentrated monofactor sera, it may be that just the antipolysaccharides. All the monofactor sera so far analysed (Wellcome) 1,2,4,5,8,9,20 are full of proteins left by the bacteria used for absorptions; due to these proteins, the presence of which may be meaningless for the agglutinations, strong precipitations in agar-gel were obtained between monofactor sera and different antibacterial and anti-protein sera containing antibodies induced against the corresponding free proteins.