Background immunoglobulin-secreting cells specific for intestinal peptidoglycan-polysaccharides in mice.

Natural antibodies to soluble peptidoglycan-polysaccharide complexes (PPC) from the human intestinal flora have been found in mammalian sera. In this study the occurrence and frequency of PPC-specific immunoglobulin-secreting cells (anti-PPC Ig-SC) were determined in lymphoid organs of normal (C57BL x CBA)F1 mice. One out of 100 IgM-SC in the spleen and Peyer's patches was found to be specific for PPC. In the small intestine a small number of anti-PPC IgA-SC were present probably responsible for IgA secretion in the gut lumen since very low serum concentrations anti-PPC IgA were found. Anti-PPC IgG-SC were not detected, although some anti-PPC IgG was found in the serum. It is concluded that the spleen is the major lymphoid organ responsible for the production of natural antibodies to PPC.