Comparison of IgG and IgM Antibodies Specific for Uridine

Abstract

Uridine-specific IgG and IgM antibodies, obtained by immunization of rabbits with a uridylated synthetic polypeptide, were isolated and purified by the use of a uridine-acetyl cellulose conjugate as immunosorbent. The IgM antibodies were separated from the IgG antibodies by gel filtration on Sephadex G-200. Both antibody preparations were pure by ultracentrifugation and immunoelectrophoresis criteria. The precipitating activities of IgM and IgG antibodies were similar on a weight basis, although the equivalence zone in the case of IgM antibody is broader. I n spite of its inability to precipitate the homologous antigen, the reduced alkylated IgM subunits were still able to inhibit specifically the homologous precipitation in the U-pAla-pLys -IgG antibody system. The average association constants for uridine of both IgG and IgM a.ntibodies, measured by the equilibrium dialysis technique, were low and of a similar order of magnitude.The complement fixing ability of purified IgM and IgG anti-uridine antibodies upon reaction with the homologous antigen displayed significant differences : low complement fixation activity was found in the IgM fraction either a t 4" or a t 37", while a high activity was found in the IgG fraction a t both temperatures. The IgM fraction lost all of its ability to fix complement when the macroglobulin was reduced and carboxymethylated. PCA reaction, using a highly immunospecifically purified I9 S anti-uridine antibody, was found to be negative when assayed up to an amount of 100 pg.

Identification of Direct Hemolytic Plaques as IgM or IgG Plaques by Hapten Inhibition

“…In general, free hapten was more efficient in inhibiting the reaction with IgG than with IgM antibodies. J aton et al found, however, that the precipitation of IgG and IgM anti-uridine anti bodies was inhibited equally well by free uridine [11]. In the present experiments approximately a tenfold difference was found to exist in the concentration of hapten necessary to obtain the same degree of inhibition of hemolysis by IgG or IgM anti-NNP antibodies from the same serum with the same density of NNP on SRC.…”

“…The inhibition of the reactions of IgG and IgM antibodies by free hapten has been compared by different authors with various test systems such as hemagglutination, phage inactivation and precipita tion [9,10,11]. In general, free hapten was more efficient in inhibiting the reaction with IgG than with IgM antibodies.…”

“…Monovalent hapten is known to be a more efficient inhibitor of IgG than IgM antibodies in various serological tests [9,10,11]. The ratio of IgM and IgG anti-hapten antibodies has been studied em ploying hapten inhibition and 2-mcrcaptocthanol inhibition [12].…”

Studies on Human Antibodies

“…With the eluates from Jos., the concentrations of all three oligosaccharides needed for 50 % inhibition were one order of magnitude greater than with the 7G eluates. In studies in other systems, Jaton et al (50) reported that precipitation by antigen of 7M and ~G anti-uridine antibodies prepared to artificial uridinecontaining proteins was equally well inhibited by uridine, but Groff et al (51) with phenylarsonate antibodies found about 10-fold higher concentrations of phenylarsonate analogues were needed to give comparable inhibition with ~M than with 7G antibodies.…”

Avidity of antibodies in sle

“…The severity of the disease, including lupus nephritis, correlates well with the presence of 7s components belonging to the IgG1 and IgG3 subclasses, which are the most common and have the most efficient complement-fixing activity (6,8). As measured by hapten inhibition studies (9,10), 7s antibodies have a higher affinity for DNA than d o 19s IgM antibodies.…”