The neonatal Fc receptor, which is encoded by Fcgrt bound non-covalently to beta-2 microglobulin, facilitates the uptake of IgG through intestinal epithelial cells, protects IgG and albumin from degradation, and is involved in clearance of amyloid beta peptide from the brain. Mice that are homozygous for Fcgrttm1Dcr, a knockout allele, are viable and fertile. No Fcgrt gene product (mRNA or protein) is detected by quantitative PCR analysis of liver cDNA or Western blot analysis of small intestine from homozygotes. Homozygotes exhibit plasma albumin concentrations approximately 45% of levels observed in wildtype controls, reduced IgG levels and diminished perinatal maternal IgG transport. Fcgrttm1Dcr homozygotes are resistant to experimentally induced, serum-transfer autoimmune arthritis, as well as experimentally induced bullous pemphigoid, pemphigus foliaceus, and pemphigus vulgaris. Homozygotes are more sensitive to experimentally induced Lyme's disease arthritis, with more severe ankle swelling, joint involvement and decreased serum levels of anti Borrelia burgdorferi antibodies. IgG is accumulated in the glomerular basement membranes of aging mutants, and clearance of IgG from the kidneys is impaired.
In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. This is the case for the strain above. It should be noted that the phenotype could vary from that originally described. We will modify the strain description if necessary as published results become available.
