title: Human secretory component. IV: Antigenic regions involved in in vitro binding to dimeric IgA.
abstract: The aim of this report was to identify the region(s) of the secretory component (SC) molecule involved in in vitro binding to dimeric IgA. Inhibition of the SC binding was tested by Fab' antibody fragments directed against the accessible (A) and inaccessible (I) regions of SC. Antibodies directed against the main 38.5-kDa trypsin fragment of SC, and antibodies from two immune sera with a wide anti-SC spectrum, were also used. The specificity and activity of the five antibody preparations were established by double-diffusion in gel and by their SIgA combining capacity. Inhibition curves were established by RIA using constant amounts of 125I SC, dimeric IgA and increasing quantities of the various Fab' antibodies. These results indicated involvement of a larger part than the I region of the SC molecule in combination with dimeric IgA, perhaps including a second (minor?) site of binding on the accessible parts in addition to the major region located on I.
mesh_terms: D000918:Antibody Specificity; D001665:Binding Sites; D001667:Binding, Competitive; D000939:Epitopes; D006801:Humans; D007070:Immunoglobulin A / Q000378:metabolism*; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments / Q000276:immunology*; D011485:Protein Binding; D012635:Secretory Component / Q000276:immunology* / Q000378:metabolism
chemical_list: D000939:Epitopes; D007070:Immunoglobulin A; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments; D012635:Secretory Component