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Panose (O-α-D-glucosyl-(16)-O-α-D-glucosyl-(14)-α-D-glucose) and maltose (O-α-D-glucosyl-(14)-α-D-glucose) coupled to bovine serum albumin (BSA) by means of an azophenyl linkage provided the synthetic antigens panosyl-BSA and maltosyl-BSA, used to examine the anti-hapten specificity of rabbit sera prepared against panosyl-BSA. The combining site specificity of cross-reactive antibodies in carrier-absorbed anti-panoside sera was investigated by quantitative hapten inhibition of maltosyl BSA-anti-panoside cross-precipitation and compared with data obtained by inhibition of homologous precipitation. Immunochemical data obtained demonstrate a heterogeneity in the combining site specificity of anti-hapten produced in response to panosyl-BSA and establish the occurrence of at least two distinct kinds of antibody directed against the α-(16)-α-(14) sequence of glucose units. One type of anti-panoside, inhibited more effectively by isomaltose than by maltose, shows isomaltose end group immunodominance. A second type of anti-panoside, cross-precipitated by maltosyl-BSA and more effectively inhibited by maltose than by isomaltose, shows maltose immunodominance.

Panosyl-BSA, a synthetic sugar-azoprotein conjugate consisting of the trisaccharide panose (glucosyl α-(1,6)-glucosyl-α(1,4) glucose) coupled to bovine serum albumin by an azphenyl linkage, cross precipitates antibody from types II and XX antipneumococcal horse sera. Hapten inhibition indicates that these cross reactions of synthetic antigen are mediated by the α-isomaltosyl moiety of the introduced panosyl haptenic grouping. While interaction of conjugate with horse anti-XX involves a fraction of antibody directed against an α-isomaltosyl end group, interaction with horse anti-II involves a fraction of antibody directed against the α-isomaltosyl end group. Purified fractions of antibody, cross reactive with panosly-BSA were specifically from antipneumococcal horse sera and their behavior with homologous antigen examined and compared with unfractionated serum.

The trisaccharide panose, 6- O - α -d-glucopyranosyl-4- O - α -d-glucopyranosyl-d-glucose, coupled to bovine serum albumin (BSA) via an azophenyl linkage was used as an artificial antigen to immunize rabbits. Antisera rendered specific for the introduced haptenic grouping by absorption with whole calf serum were studied by immunodiffusion, quantitative precipitation and hapten inhibition. Anti-hapten showed a specificity directed against the introduced p -phenylazo- s -panoside group. Hapten inhibition assays employing various di- and triglucosides, including two structural isomers of panose, established the relative importance of an α-configuration and a nonreducing terminal (1,6)-(1,4) ordered sequence of glucoside bonds for optimal interaction with antibody. A heterogeneity in the specificity of antibodies formed in response to s-panosyl-BSA was evidenced from cross reactions obtained between anti-panoside and various sugar azoprotein conjugates.

The immunosuppressive activity of normal mouse serum (NMS) was evaluated by enumeration of primary in vitro plaque-forming cell response produced by normal spleen cell suspensions in response to sheep erythrocytes. The site of action of the inhibitor(s) was shown to be at the level of adherent cells since incubation of this cell type with NMS could reproducibly inhibit responses, whereas, in appropriate experiments, incubation of nonadherent cells with NMS had no effect. Furthermore, addition to normal spleen cells of excess spleen-adherent cells, normal peritoneal adherent cells, or of 2-mercaptoethanol could abrogate the inhibitory ability of NMS. Addition of excess nonadherent cells under the same conditions had no influence on inhibition. NMS was also shown to decrease the number of cell clusters, hemolytic clusters, and the number of nucleated cells recovered upon culture termination. It is suggested that NMS, acting on the adherent cell may hinder cell-to-cell contact and interactions.