Human IgG1 kappa Isotype Control

Camel antibodies have been widely investigated, but work has focused upon the unique heavy chain antibodies found across camelid species. These are homodimers, devoid of light chains and the first constant heavy chain domain. Camelid species also display conventional hetero-tetrameric antibodies with identical pairs of heavy and light chains; in Camelus dromedarius these constitute 25% of circulating antibodies. Few investigations have been made on this subset of antibodies and complete conventional camel IgG sequences have not been reported. Here we study the sequence diversity of functional variable and constant regions observed in 57 conventional heavy, 18 kappa and 35 lambda light chains of C. dromedarius and Camelus bactrianus. We detail sequences of the full kappa and lambda light chain, variable and CH1 region for IgG1a and IgG1b and the CH2 and CH3 region for IgGa. The majority (60%) of IgG1 variable region sequences aligned with the human IgHV3 family (clan III) and had leader sequences beginning with MELG whereas the remaining sequences aligned with the IgHV4 (clan II) and had leader sequences beginning with MRLL. Distinct differences in CDR length were observed between the two; where CDR1 was typically 5 and 7 residues and CDR2 at 17 and 16 residues, respectively. CDR3 length of IgHV4 (range 11 to 20) was closer to that typical of VHH antibodies than that of IgHV3 (range 3 to 18 residues). Designed oligonucleotide primers have enabled identification of paired heavy and light chains of conventional camel antibodies from individual B cell clones. (C) 2014 The Authors. Published by Elsevier B.V. All rights reserved.

A fully human IgG1 kappa antibody (MDE-8) was generated, which recognised Fc-gamma receptor IIa (Fc gamma RIIa) molecules on CD32 transfectants, peripheral blood monocytes, polymorphonuclear cells and platelets. This antibody blocked Fc gamma RIIa ligand-binding via its F(ab')(2) fragment. Overnight incubation of monocytes with F(ab')(2) fragments of MDE-8 leads to a c. 60% decrease in cell surface expression of Fc gamma RIIa. MDE-8 whole antibody induced a concomitant c. 30% decrease of Fc gamma RI on THP-1 cells and monocytes. In humans Fc gamma RIIa plays an important role in the clearance of antibody-coated red blood cells in vivo. As an equivalent of Fc gamma RIIa does not exist in mice, the in vivo effect of MDE-8 was studied in an Fc gamma RIIa transgenic mouse model. In these mice, antibody-induced anaemia could readily be blocked by MDE-8. These data document a new human antibody that effectively blocks Fc gamma RIIa, induces modulation of both Fc gamma RIIa and Fc gamma RI from phagocytic cells, and ameliorates antibody-induced anaemia in vivo.