title: 'Background' Ig-secreting cells in pregnant germfree mice fed a chemically defined ultrafiltered diet.
abstract: During syngeneic pregnancy the numbers of 'spontaneously' occurring ('background') Ig-secreting cells were determined in the spleen, bone marrow (BM) and mesenteric lymph nodes (MLN) of BALB/c mice that were kept under germfree conditions and fed a low molecular weight synthetic diet (GF-CD), SPF BALB/c mice fed autoclaved natural ingredient (SPF-NI) and conventional BALB/c mice fed natural ingredient (CV-NI). 'Background' Ig-secreting cells were enumerated in the protein A plaque assay and the specificity repertoire of the IgM-secreting cells was determined with plaque assays specific for differently haptenized sheep red blood cells (SRBC). The numbers of 'background' Ig-secreting cells, especially the IgG- and IgA-secreting cells, are very much reduced in the BM and MLN of GF-CD mice as compared to SPF-NI and CV-NI mice. During pregnancy the total number of Ig-secreting cells increased in all lymphoid organs tested, but the proportional increase was most prominent for the IgG- and IgA-secreting cells in the BM and MLN of the GF-CD mice. This increase could only be due to their pregnant state since all environmental antigenic influences are excluded in GF-CD mice. No changes were found in the background specificity repertoire of the IgM-secreting cells during pregnancy. This suggests a polyclonal activation of the Ig-secreting cells during pregnancy. The reason for this activation remains obscure, but it has to be endogenous. Pregnancy apparently induces a new steady state of the immune system, which can be most properly investigated in GF-CD mice.
mesh_terms: D000818:Animals; D000921:Antibody-Producing Cells / Q000276:immunology*; D004032:Diet; D005260:Female; D005856:Germ-Free Life; D006462:Hemolytic Plaque Technique; D007075:Immunoglobulin M / Q000032:analysis; D051379:Mice; D008807:Mice, Inbred BALB C; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000276:immunology*
chemical_list: D007075:Immunoglobulin M