Thenatural antibody response toE.coli includes antibodies oftheIgDclass

SUMMARY Antibodies toE.coli oftheIgM,IgGandIgAclass arereadily demonstrable innormal human serum. Using thesensitive redcell-linked antigen-antiglobulin system, ithasbeendemonstrated that antibodies oftheIgDclass arealso part ofthis normal response. TheIgDantibody titre is lowandoften could only bedemonstrated inpartially purified IgDpreparations. Theavailability ofpurified IgDparaproteins andtheir Fab, andFc6fragments, aswell asantisera specific for these fragments, allowed thenecessary critical specificity controls tobeperformed.