work catalyzed an avalanche of studies that have allowed the elaboration of the FcγR family of proteins, now known to consist of several genes (8 in human, 5 in mouse), over 20 transcripts, and at least 9 expressed protein receptors; further, it has become clear that clustering of these receptors results in a variety of biological effects such as superoxide and cytokine output, cell-mediated killing, endocytosis, all resulting in removal of the antigen and perversely in disease-causing auto-immune effects. 2. IgG turnover mediated by the neonatal Fc receptor (FcRn) Anderson, reading the published work of others describing IgG deficiency in the beta2-microglobulin knock out mouse, realized that this strain was likely IgG deficient not because of low IgG production but because of rapid IgG degradation due to an FcRn deficiency. He formally affirmed this explanation by measuring the serum IgG decay rate in this KO strain. Brambell's prediction of the 1960s was thus confirmed, that a single Fc receptor served both to transport IgG across the placenta and to divert IgG from degradation. This high affinity characteristic of IgG for FcRn is exploited by the drug industry to prolong the lifespan of protein drugs. 3. Albumin homeostasis mediated by FcRn. Anderson observed in vitro in detergent solution that albumin co-purified with a soluble variant of FcRn in roughly equimolar proportions, and realized that FcRn likely prolongs the half-life of albumin as it does IgG, thus explaining the lengthy lifespan of albumin in humans and lab animals. He formally affirmed this conclusion analyzing albumin decay in b2m and FcRn KO mouse strains, and then showed that the two ligands bound to FcRn at different sites, independently, that the stoichiometric ratio of the IgG:FcRn:albumin interaction was 2:1:1, that comparison of the published sequences of FcRn in many species suggested that albumin bound to FcRn near the A peptide pocket, that the site on albumin responsible for interaction was the III domain. Co-crystal studies by others have confirmed these conclusions. Kinetic studies indicate that the evolution of FcRn was a great boon to metabolic economy: Were it not for the presence of FcRn the mouse would require a liver twice as large and an immune system five times larger to maintain albumin and IgG concentrations The albumin-FcRn interaction described by Anderson has also been exploited by the pharmaceutical industry to prolong the lifespan of protein drugs. 4. The removal of small particles from