Structural integrity of host defense factors in dental plaque.

The structural integrity of immunoglobulin A (IgA), IgG, and IgM and lactoferrin in dental plaque fluid samples from two populations of Colombian children with contrasting levels of dental caries was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by electrophoretic transfer to nitrocellulose. The immune factors or their fragments or both were detected with monospecific antibody conjugated with horseradish peroxidase. All the immune factors examined were extensively degraded, although there appeared to be small amounts of intact IgA and IgG in some samples. Analysis of the samples with antibody to secretory component showed that secretory IgA as well as serum IgA was degraded. IgG appeared to be cleaved into two major fragments, one fragment having a relative mobility similar to the F(ab')2 fragment of IgG and the other a relative mobility slightly greater than Fc. IgM and lactoferrin were virtually completely degraded. There was no apparent relationship between the fragmentation patterns of IgA and IgG in the plaque fluid samples from the two communities and their susceptibility to dental caries.