The binding affinity of human IgG for its high affinity Fc receptor is determined by multiple amino acids in the CH2 domain and is modulated by the hinge region.

Abstract

SummaryA family of chimeric immunoglobulins (Igs) bearing the murine variable region directed against the hapten dansyl linked to human IgG1, -2, -3, and -4 has been characterized with respect to binding to the human high affinity Fc y receptor, FcyR1 . Chimeric IgG1 and -3 have the highest affinity association (Ka = 10 9 M -1), IgG4 is 10-fold reduced from this level, and IgG2 displays no detectable binding. A series of genetic manipulations was undertaken in which domains from the strongly binding subclass IgG3 were exchanged with domains from the nonbinding subclass IgG2 . The subclass of the C 2 domain was found to be critical for determining IgG receptor affinity. In addition, the hinge region was found to modulate the affinity of the IgG for Fc-yR1, possibly by determining accessibility of FcyR to the binding site on Fc . A series of amino acid substitutions were engineered into the C.2 domain of IgG3 and IgG4 at sites considered potentially important to Fc receptor binding based on homology comparisons of binding and nonbinding IgG subclasses . Characterization of these mutants has revealed the importance for FcyR1 association of two regions of the genetic C 2 domain separated in primary structure by nearly 100 residues . The first of these is the hinge-link or lower hinge region, in which two residues, Leu (234) and Leu(235) in IgG1 and -3, are critical to high affinity binding. Substitution at either of these sites reduces the IgG association constant by 10-100-fold . The second region that appears to contribute to receptor binding is in a hinge-proximal bend between two a strands within the C 2 domain, specifically, Pro(331) in IgG1 and -3 . As a result of f3 sheet formation within this domain, this residue lies within 11 A of the hinge-link region . Substitution at this site reduces the Fc receptor association constant by 10-fold.

Homophilic interaction of NTBA, a member of the CD2 molecular family: induction of cytotoxicity and cytokine release in human NK cells

“…To avoid possible Fc binding to Fc + receptors (Fc + R), three mutations were introduced in the hIgG1 hinge region (234 Leu 1 Ala, 235 Leu 1 Glu, and 237 Gly 1 Ala) [29]. To verify whether the amino acidic substitutions indeed abrogated the Fc + R binding, we first used non-mutated or mutated CD244 soluble proteins (termed CD244-Fc and CD244-Fc*, respectively).…”

Collagen Induces Maturation of Human Monocyte-Derived Dendritic Cells by Signaling through Osteoclast-Associated Receptor

“…The CDR of the generated mAb was grafted on a germline-encoded, human-mutated IgG1 Fc part, Fc-hIgG1.1 (15,16). Five point mutations introduced in the Fc-hIgG1.1 hinder its binding to high-affinity Fc receptors.…”

Cleavage of IgGs by proteases associated with invasive diseases

“…31,32 All of the Fcγ family of receptors can interact with human IgG1, and these interactions perhaps function to further stabilize the lower hinge region allowing an assessment of amino acid contact points between FcRs and the Fc. 33 Multiple points of interaction within the CH2 domain and FcγRs have been documented, but there is also a critical stretch in the lower hinge/CH2 region required for FcγR-binding ranging from E233-L234-L235-G236-G237-P238, [9][10][11][12][13][14][15][16][17][18][19][20][21] (EU numbering). 13 Although contact between each of these amino acids and FcRs have not been visualized directly by crystallography, mutational studies implicate a requirement for each member of this sequence.…”

“…[6][7][8] Of particular interest is that proteolytic sensitivity has been mapped primarily to short stretches of amino acids within either the upper, or perhaps more importantly, within the lower hinge/CH2 region, a highly conserved stretch of amino acids critical for binding to the Fc family of receptors. [9][10][11][12][13][14][15][16][17][18][19][20][21] Several of the proteases that are capable of cleaving IgGs within the lower hinge/CH2 are also associated with either pathogenic bacteria, e.g., glutamyl endopeptidase V8 (GluV8) of Staphylococcus aureus or immunoglobulin-degrading…”