Secretory antibody response to local injection of soluble or particulate antigens in rats

Abstract

The local antibody response to soluble (dinitrophenylated bovine gamma globulin; DNP-BGG) or particulate (DNP- Streptococcus mutans) antigens was examined in the rat. IgA and IgG antibody characteristics (concentration, activity and avidity) were determined in milk after injection of DNP-BGG or DNP- S. mutans into the vicinity of the mammary gland during gestation. More IgG antibody activity was detected in milk collected from rats injected with the soluble antigen relative to those injected with the particulate antigen using haptenated bacteriophage neutralization analysis. Analyses of milk antibody concentrations by combined immunoadsorption, elution and radial immunodiffusion confirmed the relative difference in response between the two antigens. IgA antibody levels in milk were similar in rats injected with soluble or particulate antigen (26 ±1 vs 27 ± 7 μg/ml). However, the IgG antibody levels were higher in rats injected with the soluble antigen (24 ± 2 vs 11 ± 3 μg/ml). IgA antibody concentrations in saliva, determined by an enzyme linked immunosorbant assay, were also approximately the same after injection of soluble or particulate antigen (316 ± 33 ng/ml vs 310 ± 85 ng/ml) in the vicinity of the salivary glands. IgG antibody was only detected in the saliva of rats injected with soluble antigen (128 ± 26 ng/ml). Therefore, differences in the local responses to the two antigens seemed to be confined to IgG antibody. Inhibition of bacteriophage neutralization by DNP-lysine and an analysis of neutralization kinetics revealed that IgA antibody may have a greater avidity for a multideterminant antigen than does IgG antibody in the same secretion.